soonerlover

Recently purchased a 95 z-28 convertible. Has a new GM crate motor with less than 1500 miles. Absolutely love this car, however I drove it home over 400 miles one way and it ran awesome with no issues. Have driven it the last couple days and it has stalled when sitting at a stop light. I can let it sit for about 5 mins and it will start right up. Today it stalled at a stop light and I got it started only to have it stall at the next stop light. Coasted into a parking lot and let it sit and it started and I drove it for about 30 more mins without any issues. Once started again the check engine light will be on but only for a few seconds and then goes off. I have all the paperwork that was done to this car including new fuel pump and lines. One thing that has come to mind is that when I drove it home it was at night and cooler while I have driven it during the day while it is pretty warm out. Not sure if this has anything to do with the problem. I have noticed at times that I smell raw gas but have not found any leaks and nothing is on the garage floor to show it leaking while sitting. I am not even sure where to start to try and correct this issue but I need to start somewhere so that I can drive this beauty and not have it just sitting in my garage. Any one have ideas? thanks

slick1hunting

First thing I would do is scan for codes. There is also a common "mod" of spacing the icm and coil off of the head and that helps with heat sink issues on them. I would also check fuel pressure and pay attention for rapid leakdown. I would also pay attention if any fuel is in vacuum line going to the fpr. Also if you are not aware fuel in the tank is important for cooling the fuel pump so its best to always keep it above a 1/4 tank.


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slick1hunting

4th Gen LT1 F-Body Tech Aids. this site will be very helpful if you are not already aware of it. Details on checking fuel pressure and the icm cooling mod is also on there as well as all kinds of commonly needed info.


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shoebox

^^^

OP, when the computer is trying to tell you something, you need to listen. Even if it turns out unrelated to your problem, that is where you start.

soonerlover

Thank you so much for input. Was thinking maybe optispark dist but it was purchased new with the engine in APril of this year. Will run codes and take it from there. Thanks again!

soonerlover

slick1hunting thank you so much for the site info! Just checked it out and will definitely be hitting that often!

slick1hunting

Your very welcome but the thanks and credit goes to shoebox - Rob( the guy who posted below my post). That is his website and its like the lt1 owners bible. Major props to Rob for the time and energy and money spent to help so many other people out.


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soonerlover

Yes MAJOR KUDOS to Rob! I went thru his website a ton last night! Took car in and had fuel pressure checked and it is fine. Regulator is fine. Optispark is fine. So now I am at a total loss as mechanic. Code thrown are for emissions and nothing else. Absolutely no leaks in fuel lines. Did find a small leak in a tranny seal so that is now fixed. Have driven car quite a bit today with no issues so now not sure what next. Hate to take it any distance as not sure I can trust it to not stall out. Have seen this is quite common in the 95's but have yet to find the "fix." Will keep searching and hopefully find something. Thanks guys!

smallblockhero58

Well i maybe haveing a similar situation and i need help!! I have a 95 z28. 190k miles auto. this is intermittent. car will shut off at at red light, and you can crank it back up. Also you can be cruising at 55 mph and it will stutter, and the ses light comes on about 10 sec and disappears. no problem at all with perofrmance. just ran 9.4 @75mph in 1/8. just worried about being left on side of road. Also i cant check y codes tried many of scann tool is there a way to short it out to make light flash? i dk i need help to with related topic. i was about to buy a new opti cap and water pump looked like it had some residue but no major leak. thanks

soonerlover

well I can tell you that we are now looking at the ICM and coil. I did stop by our local auto zone and had the pleasure of visiting with a gentleman that had a 95 that he bought brand new and had this same issue. After changing ICM, Opti, coils, fuel pump and the like he found out it was his VATS security system and by passed that. I have been researching and have found where that can be an issue but not sure how common of one. I did call my chevy dealer and was told it was 2-3k to fix the TDM and about fell over. SO will try other first. If I get an answer I will be sure and post.

slick1hunting

I am pretty sure the vats is not supposed to disable a car that has ran for over 30 seconds(I am no expert). I would do the icm mod(spacing it off the head). Even if that dont solve the issue it prevents some or at least lends to the parts lasting longer. As for reading codes the best way in my opinion is a $60 cable to plug into the obd port and connect to a laptop. The 93 can be read by jumper wire but only the 93. The 94-95 needs the cable and software on laptop(a free one stickied on top of this forum) and I think a couple of the others have trial versions. If I were both of you guys I would buy the cable and download the software. I would check and report all codes. I would do the icm spacing mod. While looking at cars data via laptop and cable I would look at the iac counts , and the tps volts(at idle, and smooth increase to full throttle,) I would look to see if the coolant temp sensor is reading similar to the temp guage in car(different sensors), I would look at fuel trims and o2 sensor feedback. Being able to moniter those is so helpful.


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soonerlover

well we put a few washers in to hold the ICM away from the head. Took the car out and have driven it for quite awhile and it is almost 90 and had zero issues! I am hoping that we have fixed our problem!! Will post updates over the next couple of days!

Injuneer

Generally a bad idea to hijack someone else's thread. But since you have done it......

What scan tools are you trying to read the codes with? Are you aware that although your car has a 16-pin ALDL connector like an OBD-2 car, the PCM is actually OBD-1 and must be read with an OBD-1 scan tool. Shoebox - link to his site in an above post - has a method to jumper a 12-pin OBD-1 scanner to your 16-pin OBD-2 style connectors. We also have a link at the top of the "Computer Diagnostics and Tuning" forum to free 94/95 scanning software download.

And no, you can't short the ALDL pins to flash the codes on the SES light. 1993 was the last year that worked.

soonerlover

Question on the OBD-1 issue. Is it possible to use an OBD-2 cable and attach the USB so that it may be used on laptop to run scan from downloaded software?? I have looked on information and did not see anything but could have been not looking in the right spot. Just a question that came to mind. Thanks!

slick1hunting

ALDL OBD1 OBD cable OBDI OBD2 engine codes I dont think you can use your obd2 cable but I am not certain. That link may tell you but it has the 16 pin obd1 cable as well as the 12 pin.


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