NSW Corvettes
Technical Tips => Electrical-Electronics-Air-Lighting-Guages-Security-Vacuum => Topic started by: Vettech on February 11, 2014, 12:14:06 PM
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:grr: Have 87 - was running OK - now has a rolling miss, when pushed it farts and back fires - If didn't know better I'd say the "Timing' was out - disc the timing plug, T'Light on #1 and it shows ~6degs. This is about correct. But when the plug is disc - idle drops (but tacho says ~600rpm) and it runs even worserrrrr. Put on new leads, only codes I have are variable 33, 34 & 36 - ie air too low, too high and MAF burn off issue - these reset OK. I have little hair left but am at the hair pulling stage - I can't stand issues I can't diagnose from the books and symptoms
If this was an older style motor/ignition set up, I might say it was the vacumm advance but !?!?.
May have to change my handle. Any ideas greatly appreciated. Vettech.
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Hello Vettech,
I know if you haven't driven the car for a very long time, the analog computer,may if the battery hasnt been on a trickle charger go wonky, well not run spot on. .so when you start it up its all over the place and idling up an down and give you the symptoms you have described.
I had the same issues with mine when I purchased my car cause she hasn't been driven for over 7 months even with a trickle charger.
At the moment she's running beta but still occasionally runs odd. . only constant driving has sorted this out.
Hopefully some other C4 owners can shed more light in this matter.
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Thanks 69er - The car was idle for many years - but was rego-ed again in Dec '12 and has been on many club runs etc - and has been going very well. EXCEPT for the heating issue which I have not mentioned - maybe now will be a good time. Cold the car started and ran well, run for 30mins ++ and stop and try to restart within say 15mins and it sounded like either a flat battery or it was in the process of ceasing - but the actual water / oil temps were OK. Having said that it would always start after the second or third full rotation, BUT sometimes it would give a VERY LOUD "ping" so loud it really sounded like it had hit a valve - but once running it ran well no noises or issues - power to burn. I think I will remove the Starter motor and either rebuild or replace with a reduction drive style. Also renew the main cables, lugs etc and fit a thin light weight S'Steel heat shield.
Regards. Vettech any thoughts are very much appreciated.
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OH! - something else on what you said - in a 87 and maybe all C4's the computer has what is called a "Block Learn" section in the memory - so if you wanted to go dragging - drive to the raceway disc the battery for 10-15mins - reconnect and then race it up and down the carpark or road as if dragging (6~8 times) this then tells the processor that you want that style of driving - and changes the Shift Hysteresis of the Box, the timing etc the result should be better times etc.
Sorry I digress.
Regards. Vettech.
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Your welcome. I was told by the previous owner that whilst the analog computers have there good points, they also a somewhat primitive. It sounds like your on the right track.
If you still have problems, contact Steve Rosenfeld at Rockdale as he is very knowledgeable on these units.
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Sounds awesome, and yes they do have a memory ... I was told that too, mines a 1990 Vette.
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Amate of mine who doesnt use the forum just rang and said he had that very same prob . He says its the mas air flow senser he said if you like you can ring him on 0409724442 to talk to him his name is Greg .
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Hmmm, I think I have a New Adjustable MAF Sensor laying somewhere I bought for my 1988 C4 but never used..... P.M me know if your interested ?
Jethro
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Thanks everyone - Whilst trying to sleep I had an appithany (where's the spell checker) last night and thought it may also be the ESC - Electronic Spark Control unit, but this would normally set a Code 43 - So before any more I'm off to work to download all codes - if no 43 then I will ring Greg.
More than likely your Greg is on the money since Codes 33, 34 and 36 are all MAF related issues. I've checked the associated relays and their contactor resistances and they check OK. But my gut still tells me that detonation, back fires etc upon acceleration are a function of timing, vac advance etc. So I will pack up and off to Minto to see what codes I now have - I'll try and refrain from taking the 1 gallon can of petrol with me.
Regards,
Vettech. :grr:
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If you can find someone with an 87 you could swap MAF to confirm? Apparently 85-87 are different MAF's but I have swapped (briefly) with no issues.
Here is a rare example of something that can happen (to me) with similar symptoms - my earth cable was moving an intermittently touching the exhaust. Probably not your issue but worth checking.
Disconnect your battery for 5 mins and take it for a run. If you only have the MAF related codes see if you can swap it with a working one.
I cannot see the point of a learning mode. All that data is hard programmed into the chip. It will only change if you buy the software and flash a new one.
oh, and check the knock sensor wire on the rhs of the block. Sometimes mine comes loose and cause issues.
Good luck. :cheers:
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Ok - thanks 77CVT for your reply.
I'm at work and set up to read the codes and got 33, 34, 36 aaand a 42222 what the - I expect a 43 not a 42, 43 is the EST - ie the module in the Dissy that changes the Pick Up (points) signal to drive the Primary Coil winding of the EHT Coil. Reading Manual. Ah haaa! the last time I did the Timing Light I disc the bypass or "Set Timing Connector", I must have left it open cct. No it was OK, but still had the codes - penny drops - disc battery - reconnect start codes again and sure enough all codes now reset. Start car - you can still here it running like a dog. Drive up street and give it some boot - still no codes but it is still missing and occasional backfire.
Now - 77CVT - thank you I have checked those items - the book also says check them as they are the most likely to cause issues. On ECM - yes it has a whole lot of stuff "HARD' programmed into it and you can change the chip to give other specs. But the ECM is only a Computer and can only give "X" if inputs "A ~ Y" have certain values. So a section of the memory is called "Block Learn" and as I said it sees what you are doing and sets the parameters for max power or efficiency or what ever you require - ie Dragging. BUT - this is volatile memory and if battery is disconnected the memory is wiped.
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Don't shoot me for asking :bolt: However Fuel is o.k ? :leaving:
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Ummmm! - Fuel - well there is only a range of 41Kms - so it is nearly out - this has been running like this for some time - and I'm sure it was filled at Blackheath on the return from some Bathurst Pub run, El President I think also filled up - Caltex. It drove home fine and back to the warehouse OK - and a few short runs into CBTN, then started playing up.
ONE Thing I have not done is remove the PLUGS. I replaced all leads. Took out #8, was OK - like brand new. But it was a PITA getting back in - I had the horrible feeling I was cross threading it ERRR. So I have not removed any of the others.
The fact it has still ample power and backfires when pushed could indicate one or two not firing and when the fuel gets into the exhaust it ignites - backfires.
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NO NO - I'm talking rubbish - it was refilled for the Dam Xmas run - where !?!?. But ran OK - was only back in the w'house going for a short run or a test that it started this problem prior to Xmas.
But it could be fuel - I might shout it a new fuel filter.
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NO NO - I'm talking rubbish - it was refilled for the Dam Xmas run - where !?!?. But ran OK - was only back in the w'house going for a short run or a test that it started this problem prior to Xmas.
But it could be fuel - I might shout it a new fuel filter.
And a new tank of fuel :thumb:
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And a bottle of Techron Concentrate fuel system cleaner from your local Caltex.
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And a bottle of Techron Concentrate fuel system cleaner from your local Caltex.
A Gazza Retired but still a Caltex boy through and Through :grin2:
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Caltex rubbish - poo.
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I had a dizzy module cr#p out on me half way through running in a cam! Ran like a dog - lucky I had a spare. I don't recall if it threw a code out or not.
I'm guessing it's something electrical/electronic. Pity you'r not near me or you could swap all my parts to find the problem.
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After disconnecting the battery, rather than waiting 10 minutes generally you can just press the brake pedal for a few seconds. The brake lights will drain the remaining charge from the ECU (and the radio) and erase any saved settings.
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Have found my Laser Temp Gauge, will try it tomorrow to see if an exhaust manifold is colder than the rest - I really don't want to remove the plugs unnecessarily.
And you are right about draining the power from the ECM - I bypassed this on the "KISS" principle.
Vettech.
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Caltex rubbish - poo.
Vettech, i don't know about you, but my car was tuned to run on Caltex, as i was told by the previous owner that its the most refined and cleanest fuel... for modified cars... :drag:
I use only BP in my modified TTs Audi and it runs awesome, similar with the bike.. Unless someone can recall, cause i remember this thread came up some time ago.. i will stick with my Caltex..lol :drivedevil:
M :bolt:
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So let me get this right Caltex is best , but you use BP Mmmmmm
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I used BP in my mower
It a bit hard to start now
Bfit
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Come on guys, put the thinking caps on and answer this, how many brands of petrol are sold in NSW? Now how many refineries does NSW have - Ummmm. And if you are worried about clean fuel then get a decent fuel filter. I guarantee there is not a servo in NSW with inground full tanks that are not polluted with Water, other types of fuel, sewerage and other contaminants. I know that in the days when we used heating oil in our homes, come winters end it was mixed in with Diesel fuel to get rid of it, and free the tanks/plant for other high turn over product. Diesel was so bad in the Young Hardin area it would stuff up all farm fuel pump seals unless you used the Vitron type seals. God only knows what was in that particular Diesel fuel. :omg:
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It's pouring outside and I can hardly hear myself over the din on the roof of the warehouse, time to do something else. Start car and run up for 10 mins with occasional rev up. Temps are as follows.
1=140, 3=240, 5=240, 7= 230 then 2=150, 4=250, 6=250 8=140 Ummmm!. Maybe that Gazza was on the right track - obviously 1, 2 & 8 are not firing or getting enough fuel, so I'll try a dose of something in the fuel to clean the injectors. Other scenarios (ie ECM is F#@@ed) I won't contemplate at this time. But just in case do "WE" know someone GOOD who can re-flash the Chip, that's someone we trust - I don't trust my babies most innermost parts to just any one. :banghead:
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Other scenarios (ie ECM is F#@@ed) I won't contemplate at this time. But just in case do "WE" know someone GOOD who can re-flash the Chip, that's someone we trust - I don't trust my babies most innermost parts to just any one. :banghead:
Unlikely to be an ECM causing temp variation as the odd and even cylinders are in parallel on a L98. More likely to be crappy fuel. I made the mistake of putting an ethanol boosted 100 octane in my '88 and blocked 1 & 2 so badly it run super lean and had the exhausts glowing.
On the issue of plugs, I'd carefully pull them out as colour will tell you what's happening. Difficulty with thread is common if you have aluminium heads. Withdraw in part turns then screw back between parts to clear the carbon. They'll have to come out eventually and the longer left the tighter they'll get. Clean the threads well and reinstall with an anti-sieze.
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Thanks Sabre.
It would be and to double check I redid the test several times with Batt Disc between tries, just in case there was a moving glitch - results much the same. Last night I remembered a trip Mal organized to NULON - and wallah! - the goodies bag has a bottle of "Fuel System Cleaner" - this is a product I've never had much time for - so today I'll re-fuel and add the Cleaner. It will be an interesting test and I hope it will still save me removing the Plugs. :bag:
Sorry I'm a bit slow this morning - yes yes of course, "TPI" ~ the Injectors odd , even banks are all energised at once, so gunk or faulty injector is more likely than ECM. Good thinking 99.
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WELL WELL WELL ! - I've now developed a new respect for wonder fixes in a bottle. Filled the tank and went down the Hwy, slowly it got better, stopped back firing, missing, by the time I got Picton Rd it seemed a whole lot better, went off Picton onto Menangle, even stopped at "The Menangle Store" but his divers weights were too dear now - then came back to Minto. I do believe the problem is fixed. I suppose one should not try to over think small problems. :cheers:
After that run - all cylinders seemed to be around 260 Deg C.
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Quote:"Maybe that Gazza was on the right track"
Wonder fixes in a bottle eh?
From the day that ULP was introduced onto the Australian motorist, there have been problems with gum formation on injectors, and deposits throughout fuel systems and upper cylinder areas. Techron was brought to Australia from Caltex's parent Texaco, on request from BMW and others, who had experienced the problems elsewhere in other markets. It was the first product of it's type released in Oz, and is still added to Caltex Vortex 98 petrol to help keep a clean system to stay that way. After 43 years in the petroleum business, I know the problem is real, and the fix is genuine.
What kind of pie is that you are eating Vettech? LOL. :zip:
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What a great result, maybe Nulon can use it in there adverts. Does this mean the new name is Nulon-Vettech a marriage made in a vette forum Lol, Hmmm Uncle Doug.
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I'm glad the fix was an easy one for you Doug, and your Vette is back to good health.
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Ha! You didn't think the fix was that easy DID YOU? When I started this it also had a rolling miss, so when it looked like several cylinders missing - it seemed to explain the rolling sensation. WRONG. When I got back to work and checked manifold temps there was still a rolling in the idle, but when hood raised it also had a Very Horrible Loud noise. Something on the front of the engine was about to give up the ghost. One of the units was about to destroy a bearing,the run down the Hwy with the occasional squirt was enough to Bing it to a head, it never ends.
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Well I got to work and put her out in the sun and opened the hood, was about to start her up and listen, when I noticed the rear cap of the Alt was missing. No need for the Stethoscope now. I could see the hard working little ball bearings - Ummm! seems some of the balls have gone walkies. De-tension the Belt, remove three bolts, remove Alt. This was a replacement Alt back in 18.02.03, and considering the car was off the road for ~5 years not a good add for Enzo's Auto Elect.
So I need a new one, I could rebuild but the outer slip ring has been damaged, and there is no telling how much the end case has been deformed and scoured out.