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I have an 88 L98 vette stock... Have done the major tune-up include new cap, rotor, spark plugs, o2 sensor, cleaned throttlebody, replaced the IAC, checked the TPS sensor, ran fuel pressure check (off sitting still and running) etc... The problem i have is it runs great a couple days and not the next... It has great off idle response and pulling power and the next day not... Also i noticed it takes a bit to start when cold...Could one or more fuel injectors be leaking? How to check? should i leave the fuel pressure gauge hooked up over night and see what it reads? Any thoughts...By the way no codes come up...
I had a 400 small block in a 86 camaro and it would do the same thing. It would run great one day and crappy the next with the TPI. I never understood why that happened. Now it has a 830 holly and victor jr. intake and it runs great all the time while getting crappy gas mileage.
I don't know if this will help or not. I have a 88 that used to stall when hot and only in the summer time. It had a long cranking time too when hot. Since I started to disconnect the battery ( have one of those quick disconnect switches) after each time I use the car all my hard start and stalling problems are gone. I think what happens is that after each time you disconnect the battery the computer has to reset certain functions and I think that it has reset the IAC motor (moving and freeing up the piston or whatever moves up and down inside of it that might have got stuck from carbon or lack of use- only 30K miles now) Maybe a simple thing like disconnecting the battery for several cycles will help? Cheap fix to give a try. Good luck
PS I would think that if an injector was leaking that would not effect a cold start as all the fuel would be out of the cylinder after an extended time? It surely would effect the hot start which is not a problem? There was also a service bullitin about one of the relays causing hard hot starts- maybe someone knows more about this? If I recall right there are two that are mounted on the driver side firewall that they were talking about.
It only starts hard when it's cold...If this helps, It started up fine right out of storage and just brought it home...Never started again till next morning. Had a hell of a time firing up. After that it started but not as long...
Re: What could cause this problem ??? (jackdaroofer)
I had it over winter for 5 months. Had fuel stabilizer in it also... Been driving it for 3 weeks or so with a couple fill-ups all ready and still notice this. P.S. had the same thing go on last year but it does it more regularly now. Idles great all the time though and gets 26-29 mpg on the highway.
I haven't yet and i've owned it 2 years...Not sure what was done before that. Would that give me a occational problem ? One day it has great throttle response and the next day not so good... Doesn't matter if i have a full tank or not.
I think your 88 has a cold start injector on the left side between the runners. If that isn't your problem, then I would suspect a fault in the EGR system.
Also i noticed it takes a bit to start when cold...Could one or more fuel injectors be leaking? How to check?
You're cold start injector might be bad. Mine is and I can't find a replacement for it. You're injectors could be leaking too. You will need an injector tester, a gauge and hose with fitting to check your fuel pressure and leak down rate and an amp meter to test each injector.
I replaced my injectors at 85K miles. You might look at Summit racing and their Ford injectors. I think you can get 8 for less than $300. and from what I've been told by a couple of Vette mechanics they are bullet proof. I didn't know this and I bought Borg-Warner injectors. I have 72K on these. I'm starting to see longer than usual cranking times when the engine is cold so it's time to test these injectors and maybe replace them.
I think your 88 has a cold start injector on the left side between the runners. If that isn't your problem, then I would suspect a fault in the EGR system.
He said he doesn't have any codes. I received codes when my EGR would stick due to carbon build up. It sounds more like his cold start valve between #3 and #5 cyl.
If you know where one of these can be found let me know. Mine is shot and my Vette dealer's parts department says GM doesn't make them any more. I've tried Pep Boys and a couple of other places with no luck. :(