Cornholio7979

iTrader: (1)

My 89 5.7 IROC has been getting progressively worse over the course of a few years. I had the engine rebuilt (I'm doing it myself and buying all the damn tools for the next one) and replaced nearly every sensor about 3 years ago due to head gasket failure and was told no boring had to be done because the cylinders were so clean. Engine has functioned just fine for about 2 years and a year ago started acting strangely.

I remember getting 16-18 mpg with my driving with mostly city miles before I had to rebuild. Now I max out around 13 mpg... I feel this is connected now. I've been data logging randomly over the past couple of months and found a few red flags. The thing that really caught my eye was a consistent BLM of 150-160 which I know is an issue. I just can't figure out why since even the Helm manual I picked up has no info on it.

I have also recently had a code 22 (TPS low voltage) going off intermittently and I can't see in my logs how low it got, or even find online what exactly that means since it seems to be set properly.

I am having issues with my alternator providing low voltage to the car that might correlate with the code 22 as my original alternator is an aftermarket hi power unit that failed and I don't remember my spare stock alternator having this issue before, but it's been a few years since I used it.

I also have hard starts when the engine is cold and this wasn't always the case. I usually have to crank for a few bursts of 5-8 seconds until it finally comes to life. Once warmed up it will start up fine.

I have funky starts when the engine is hot. I have to feather the gas while the engine sounds and feels like its running on half the cylinders and gives a backfire every once in a while. Once I can get the RPM steadily past 2k, it smooths out for the most part and I can drive it.

I feel like something is telling the ECM to dump too much fuel, causing my bad MPG and unnecessarily heating the engine up so the hot funky restarts occur. Why exactly it has cold hard starts, I'm still confused about.

I've installed the following within the past 1-2k miles: new spark plug wires, plugs, cap, rotor. I'm also including some recent TunerPro logs (zip file since xdls won't work) in the hope (expectation really) that you know more than I do and see what's wrong or at least give me a direction to go in.

-Cornholio

aliceempire

iTrader: (14)

You gave a whole lot of info and missed a whole lot too. I'd personally start at the basics. Fuel pressure? What injectors? How old injectors? What did the old plugs look like? What do the new ones look like now after running? Timing? Do you have strong spark?

fltche1

I am having simillar problems and his symptoms basically match mine except for the code 22 and the alternator voltage issue. If his plugs are anything like mine then they will be covered with crud. Not all of the plugs were as bad as the others. The two cylinders closest to the firewall were gummed up pretty badly in my case. It would be well worth checking the condition of you plugs. So far my guesses are on a bad injector or possibly dead piston rings in a cylinder or two. Would a bad valve possibly be a culprit in this scenario? But I would definitely check the spark first. An incomplete or poor spark will make any car run poorly. I changed my plugs when it first started running rough and it ran great for a week and a half. So definitely what Aliceempire said... Check your plugs. You can even check your fuel injectors with a Volt meter. I have the factory manual and the information to do that. I will be checking mine tomorrow / this evening (so long as it isnt another torrential downpour here).

fltche1

Found this on another thread that would be an easy check as well.

"I had similar issues recently, it was a bad TPS. My car felt like it was slightly out of timing. Poor throttle response and shook like it had a cam. Its easy to check the tps, get a volt meter, turn on ignition (dont start it), stick the (+) on the volt meter in the center wire on tps and (- ) ground on the engine. It should read .54v closed and over 4v at wot, voltage rising evenly as you open the throttle. "

Cornholio7979

iTrader: (1)