My 95 camaro z28 has a rough idle and boggs out when excelerating! Pelase Help!

[legendkiller5150]

I recently purchased a 1995 camaro z-28 with the lt1 motor. It passed a inspection and the Smog test before i picked it up. When i started it i noticed a rough idle. It was at about 800-900 rpm's in park, and about 600 in drive. It has a real rough shaking to the idle like a miss or something. He immediatly said, durring the ispection the shop said it might need a fuel filter because it was stock. I drove it home and noticed it was hessitating or stummbling realy bad when i would give it gas, but when i was cruising on the freeway it ran fine??? Once i found the spot on the pedal where it wouldnt bogg out i could keep my foot steady and it would run smooth, but as soon as i stop at a light the idle gets rough and it boggs out when taking off from a stop, or giving it gas? It runs at a super cool temperature, normally at about 160 degrees but when i stop at a drive through and the car isnt moving it seem to heat up realy bad. (240-260 degrees) As soon as i get back on the road the temperature drops back to 120-160 degrees? I just changed the fuel filter which was not stock, and fixed a small vacume leak I found and it helped but it is till pretty bad!! I pray its not a cracked head gasket, head or block! I have been hearing they probebly set the timing low to pass smog and that might be it? Please help. I just bought the dam thing this week! I just cant see how it could pass a inspection and smog and run like this??

[Rally Sport]

Okay this really sounds like your Ignition Control Module or your throttle position sensor, but youd notice if it was the TPS if you hit the gas but it doesnt accelerate like it usually would. But the rough idle sounds like the ICM.

[legendkiller5150]

I just went outside and made sure, and the oil looks good and fresh, and the water is fresh with no slude or oil! Good signe its not a cracked head or block I guess? Oh by the way, there is a warning light on all the time? Its a red light in the middle of the dash and it looks like some type of a water or fluid guage? I have a new radiator, and its full, so is the wiper fluid??? Sorry about being so lame, but I have only had old school hot rods! My newest car was a 1970 nova and Chevelle! I am new to the newer chevy motors!

[transgta]

My gta was bogging at takeoff and sometimes a rough idle. I took to pontiac they said they couldnt find a problem so i changed all sensors, injectors everything still had probs. Pontiac guaranteed me it wasnt fuel pump but hell i changed it anyway. Problem gone dammit it runs good. If you change it dont get a cheap autozone or mexican one cause you dont wanna do it again... My car only has 19000 miles on it so you never know when something can go out...

[ikeyballz]

how about the optispark?

[FormulaLT1]

I agree, sounds like the signs of a opti about to take a dump on you.

[legendkiller5150]

Sorry, this is my newest hot rod. I am use to 1970 Novas and Chevelles. I dont know what a opti spark is?? What is it, and is it expensive to fix? By the way thanks for the help guys!

[FormulaLT1]

It is the distributor on LT1's. Its called a opti spark cause it uses a optical sensor to trigger the coil based on cam timing. The design flaw with these is that the water pump located directly above with a seep hole. After the water pump starts to go and/or leaks onto the opti. Moisture builds up inside the distributor and causes corrosion and distrorts the opti reading. In most cases it just needs a new cap and rotor and a wd40 bath to clean it out and fix the problem. However if the problem has been there for a while a new opti might be required and your best bet with that is to check ebay or a aftermarket one threw a place like www.summitracing.com or maybe even a used one threw a salvage yard. Good luck

[wrightz28]

Yeah it sounds like poor ignition control or running extrememly lean.

[DVS LT1]

legendkiller5150,

What you have described is exactly how my car was running before I took her off the road and yanked the motor (don't worry I was planning to rebuild regardless lol). My problem was ignition as the boys here have just mentioned. My opti had endured a tiny yet steady stream of oil for a couple years, and one of my red MSD ignition wires had come to rest on the oil dipstick and turned grey at the contact point (cooked).

I'd check all the ignition wires for signs of heat damage; I'd assume the plugs were replaced prior to sale? The opti is definitely a bitch - hopefully you don't need to replace the entire unit but just the cap and rotor.

And you are right about these cars running fucking HOT! Mind you that's probably one of the reasons why they pass emmissions tests. Anyhow, I don't know if you are looking to modify or increase the performance of your car but I would highly recommend you go out and buy a 160 degree thermostat and have the fan settings on the computer modified - simply changing the stock 180 thermo for a 160 will not do much, you need to set the fans to come on at lower temps. For about $150-$200 you should be able to pick up a Hypertech Power Programmer which will allow you to lower the fan settigns - there's also places like PCMforless.com that you can ship your computer to and have modified (think they're $50 to program). I went and got the Hypertech unit and the difference was night and day - my car ran cold all the time. We're talking stuck in high-noon summer traffic for hours and being able to place your hand on the intake manifold and it being warm to the touch (instead of molten lava hot). It was a huge difference.

Plus there's other cool stuff on the Hypertech like the power tuning which you could try out for fun. But, if you do send out the computer for a tune you may want to consider having the idle RPM's raised. You can even get the guys at a GM dealerhip to do this for you with one of their diagnostic tools - it took my buddy 2 minutes to do it in the parking lot of his dealership.

[legendkiller5150]

Thank you guys for all your help. I drove it a little today and its much better, exept the check engine light has come on twice and then went away??? It still has some hesitation when giving it gas at a low rpm basicly. I noticed the rpms are about 200 rpms higher today and it ran way beter, but when it gets warm, the idle droppes down to 800-900 in park and at about 600 in drive. When it was at 1100 rpms at park and 700 in drive it ran way beter. The problem is that it only stays at those rpms for the first 3 minutes of driving! I thought maybe the ignition got wet and it was drying, or I did see a little smoke when it was running under the hood so maybe some oil leaked on it??? I will get some money in 2 weeks and take it to a GM dealership and get a diognostic done so I get it done right.

[DVS LT1]

Your car does that to warm up - mine would idle at 1000 RPM in park and 850-900 RPM in drive after startup. Then as soon as the engine got warm it would drop to around 800 RPM in park and about 600 RPM in drive. I always though that was way too low. I was running the Hot Cam at the time and people riding with me would always ask if my car was about to stall lol.

Wish you knew someone at the dealership you could just ask to plug in a tool and see if any error codes come up. They'll probably ding you for a $45 or $75 diagnostic fee but if it helps identify a problem thats a start. Whatever you do don't let the dealer suck you in to buying the parts from them. A new optispark from a dealership will cost twice as much as it would to order from www.gmpartsdirect.com ($276 online vs. $500+ from dealer - PN # 1104032). I've seen new Accel aftermarket performance replacement opti's on ebay for $230, supposedly even more reliable than factory unit.

I'd start simple and cheap though - replaced plugs if its been a while, then check and replace ignition wires if necessary, then determine if its the opti and whether just the cap & rotor needs replacing or the whole unit. Could even be a bad ignition coil perhaps?

Good luck.

[DaytonZ28]

I am having the same problem so far the water pump and opti have been changed along with plugs and wires. I have read about it possibly being the ICM does anyone know if this could be it or successfully solved the problem?

[BentleyRussell40]

I would suspect the TPS. Have you been able to eliminate that as a source of the problem yet?

[Tech II]

I sure hope he has that fixed by now.....