'94 S10 Blazer CPI starting problem

bcny168 · #1 08-30-2012, 12:53 PM

Hi guys,

I've done a lot of reading to see if I could find a solution prior to posting this message. I have a '94 S10 Blazer CPI with 220K miles on it. Recent things done to it were, New spider with regulator, nut kit, intake manifold gaskets, spark plugs, rotors. No fuel leaks in intake plenum and fuel pressure is holding at a steady 60psi and when key off for a few seconds would hold 55psi. Car runs fine before.

Problem is I haven't driven it for a month and when I went to start it, I need to step on the gas pedal to start it and the idle speed would surge up and down, up and down continously looking to shut itself off. Seems like a vacuum leak but I checked all the hoses and it seems fine. If i put it in reverse, it dies. I could drive it but it would stall when I come to a stop light unless i keep my foot on the gas pedal. When I'm driving it, the surges does not happen at all, it happens only in park gear. Do you guys have any suggestions on this problem? I did notice the throttle cable is a tad too loose but don't think it is adjustable. Could that be causing my idle problem?

I tested the TPS and the readings look ok. Can the Idle air control valve be causing this problem? I didn't see where this valve was when I looked near the throttle. Any advice is appreciated and thanks for the attention --Barry

jdl · #2 09-14-2012, 12:06 PM

Yeah, my thought was to check and clean the idle air system. Any applicable trouble codes? Automatic tranny at idle in drive--550 rpms. Iac count 5--40.

NHRA · #3 09-14-2012, 10:34 PM

check your egr valve <<<<<<<<<<<<<<<<

bcny168 · #4 09-24-2012, 08:33 AM

hello,

checked the fuel pressure again and its good running and when i turn the car off. i also replaced the egr, throttle position sensor and idle air control valve. problem is still the same. Now I can't even step on the gas to start the car. so i put all the old parts back and really deep cleaned the egr again. after numerous attempt to start it and it wouldn't start, i waited a few hours and it started (without needed to step on the gas) with the same symptoms i mentioned on the thread before. It surges up and down and will shut itself off if i put it into gear.

i'm beginning to wonder if it's the ignition coil or control module but then it'll start after a few hours but surges up and down. older posts mentioned it could be the alternation but I'm getting 14V at the battery consistently even during the surges and battery is new. i'll try to replace ignition stuff and report back. thanks for the attention.

cpi, regulator, line kit, rotors, plugs, cap are all new. i might just junk it if all else fail.

autojoe · #5 09-25-2012, 08:51 AM

what is your cranking fuel pressure?bleeds down 5 psi in 2 seconds.bleed down should be 5 psi in 20 minutes most time not even that.what is bleed down after that?if you spray some carb cleaner into intake does it start?try that.60 psi should be enough to start unless pressure is bleeding down too much.

bcny168 · #6 09-25-2012, 08:23 PM

Thanks for the response. Cranking was around 60 and then 55-50psi for close to 10 minutes after shut off. It cranks for a long time and would like after 40 seconds. I tried spraying carborator cleaner in the throttle but it actaully makes it worse and won't start until hours later. any advice is appreciated. thanks.

autojoe · #7 09-25-2012, 08:48 PM

take iac off and check for carbon buildup.any carbon on butterfly?a scan tool would be nice to look at data pids.....especially iac and short term and long term fuel trim.is your idle rpm lower than usual?smoke machine is the best way to detect vacuum leaks.nhra stated egr valve......did you check.

bcny168 · #8 09-25-2012, 10:49 PM

Quote:

Originally Posted by autojoe

take iac off and check for carbon buildup.any carbon on butterfly?a scan tool would be nice to look at data pids.....especially iac and short term and long term fuel trim.is your idle rpm lower than usual?smoke machine is the best way to detect vacuum leaks.nhra stated egr valve......did you check.

yeah i replaced the IAC, and EGR and the butterfly is very clean. i didn't see the engine light come up but will try to get a scanner to look at it. the car doesn't have a rpm guage but when i get it to start, it idles up and down but doesn't shut down unless you put it in gear.

autojoe · #9 09-26-2012, 08:53 AM

the hunting idle is all the time with engine hot or cold?have you looked at your 02 signal volatage with engine hot at 2000 rpm?should be switching high and low.if your rpm is too low it will stall when placed into gear.check your charging voltage and see what it is doing.I assume you have a dc multimeter.fuel pressure cranking is 60 and after it starts is what?snap throttle it should increase above 60 and decrease around 58 and then recover to 60.bleed to 55-50 after 2 seconds seems a little much.a good scan tool is very valuable....not a code reader.....they are pricey but can get a used one on ebay.I have 3.primary is a snap on solus pro.I stated early post about stft and ltft that is obd2 96 and up this would be gm intregator and block learn multiplier.this tells computer to add or subtract fuel by altering the pulse width or on time of the injectors based on rich or lean conditions.

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