Mechanics- fix my Chevy! Intermittent 93'

[CrawlinMike]

I wouldn't normally post in chit chat, but looking on Chevy forums they look terribly slow. -- ok problem--
93 c1500 w 5.7 v8. Always ran fine. Normal for check engine light to come on occasionally. The last few months at random times the idle ticks higher and it'll run different all at once. Like the timing changes. If you blip the throttle it completely cuts out and seems to run rougher. When this happens my trans acts like it's going out. It waits way too long to shift even babying the rpms up. Normally I'd think the trans was going out but since the motor acts so stupid at the same times it must be something else. If I shut it off a few minutes it'll be normal awhile again. And sometimes still be there. Before this gremlin shows up she shifts and runs perfect.

What sensors should I try to change? Or insights? Thanks fellas.

[1tonscout]

I would scan the codes before assuming a sensor is bad. It may be as simple as a misfire/bad coil pack

[CD13]

First one I would look at is the EGS at the cat.

[CrawlinMike]

Well there hasn't been a cat on it for years... Soo. That's out haha. When the problem comes up its constant and consistent until shut off again awhile. I will try to read what codes it throws next time. It's the old count the blinks type. I'll have to google to remember how to do it again and the codes themselves. Been years since I read codes on an old school.

[b00st3d-vr6]

ignition control module on the distributor was acting up on mine, sounds like a similar issue on yours. i believe the module is like $40 most auto parts stores have them in stock and it takes about 15 min to change.

[Sevastra]

Pull the cap and rotor, check for corrosion build up on both. You'd be amazed what problems it'll cause, even if you have good plugs and wires.

Afterwards, start double checking your ground wires.

[Crank]

I had a 94 fullsize blazer with an identical issue, after replacing the throttle body, throttle position sensor, egr valve, cap, rotor button, wires, and ignition control module.
The icm made the most improvement, but after all that work and a new 480lE trans (that stupid E adds a lot to the cost) I sold it and cut my losses.

One thing I never tried, but after talking to other people I should have was a ground issue.

[offroadace]

Fuel filter/line? Clogged/air?

[robertjpjr]

Does it have a BEC?

[CrawlinMike]

Alright guys got some good old fashioned code pulling done. Starts w a 12 as it should, then moves onto 22(throttle position sensor) and then onto 32(egr). Yall have been good. Guessed on those and codes seem to agree. I'll report back after the changes. Although may not be today. Look I even found a code key! Not needed but amazed I came up w it.

[CrawlinMike]

Originally Posted by offroadace

Fuel filter/line? Clogged/air?


]

A pretty new Fram air filters on there. At this point I can't rule out fuel pump/clog but it's low on the list. No fuel smell around. Still I'll see.

[KJ10]

EGR was gonna be my guess. I had a 93 Dodge that had the exact same issues. A new transducer in the EGR fixed it. Didn't need the whole valve, thankfully. That would've cost about $100 more than just the transducer.

TPS is also a common failure point, for that era, from what I've heard/read.

[CrawlinMike]

Ah just because a pictures worth 100o words here's a clip when I got home and it had entered retard mode. Up until the problem starts it runs perfectly. This is the throttle bog during. Here I'm just blipping the throttle a few times and you can hear it's like the timings set off. Be digging in soon.
http://youtu.be/ZHY0TkrIndQ

[BigSki]

TPS was going to be my suggestion. I had a '94 K1500 that had identical symptoms. After a bunch of OBD-I trouble shooting, it was the TPS. A volt meter was used to test it, it was 'worn out' in the middle of the range, causing a unstable voltage signal to be sent back to the 'puter.

[snapon boy]

Even though you may not have gotten a code clean or replace your oxygen sensor/sensors and also clean the mass air flow sensor. They make a rattle can cleaner that is safe for both. Some of the egr value assemblies can be cleaned. My avalanche had similar issues and the above helped. However I found that my plastic intake manifold was cracked. IMHO

[Sevastra]

EGR valve sticking open will cause rough idle and lack of power. Combine that with your TPS code and I see a bad combo.. Take care of those two first.

[CrawlinMike]

GENTLEMEN!!! Throttle position sensor replaced and that has to of been the problem. I've put up with this well over a year. A little over $40 and 15 minutes of replacing. Drove 10 miles or so in town and 3 or so on the highway. Shifts sooner than it used to too. No engine light, no tranny waiting to shift till 3k, and no engine hesitation. Smooth sailing. If that's all it was I'm pretty damn glad I didn't put hundreds or more into it.

[hotrodsonoma]

I would have guessed MAF(Mass airflow sensor) our car had a dirty one(Doing similar)took air compressor,blew it off(wires)mainly and idle went back down.