88 chevy k1500 PLEASE HELP!!!!!!!!!!


ironhand33
03-09-2009, 05:47 PM
I have an 88 chevy K-1500 4x4 5.7L ... My truck lacks serious power, it idles rough, sometimes wont idle at all, sometimes Truck Idles fine. I have adjusted the timing to tdc, and 4 deg. both ways still runs like crap.. Sometimes I can keep it idleing, put it in rev. or drive, and it will die. I have no power and if I put my foot in it too much it will backfire. but will only backfires when in gear and press on the gas to put a load on the motor. I have replaced the: tps, map, egr, pcv, distributor, cap, ignition coil, rotor, plugs, wires, timing chain, both sprockets cam and crank, checked all hoses for leaks, replaced the injectors, the O2 sensor and have changed the intake gaskets. And am still having no luck...... I am bout to just drop an M80 in the gas tank and watch her burn.. Any Any Any suggestions would be appreciated...... I dont care if its probably the dumbest suggestion you have ever thought of, ie change the blinker fluid...:eek7: yeah shoot all of them at me....

Thanx for any suggestions. Allen

MT-2500
03-09-2009, 06:44 PM
I have an 88 chevy K-1500 4x4 5.7L ... My truck lacks serious power, it idles rough, sometimes wont idle at all, sometimes Truck Idles fine. I have adjusted the timing to tdc, and 4 deg. both ways still runs like crap.. Sometimes I can keep it idleing, put it in rev. or drive, and it will die. I have no power and if I put my foot in it too much it will backfire. but will only backfires when in gear and press on the gas to put a load on the motor. I have replaced the: tps, map, egr, pcv, distributor, cap, ignition coil, rotor, plugs, wires, timing chain, both sprockets cam and crank, checked all hoses for leaks, replaced the injectors, the O2 sensor and have changed the intake gaskets. And am still having no luck...... I am bout to just drop an M80 in the gas tank and watch her burn.. Any Any Any suggestions would be appreciated...... I dont care if its probably the dumbest suggestion you have ever thought of, ie change the blinker fluid...:eek7: yeah shoot all of them at me....

Thanx for any suggestions. Allen

Things to check.
EGR valve stuck open?
Good Hot blue spark to all plugs.
Good Fuel pressure?
Good compression and ac delco plugs and good plug wires not crossed?
Dist cap and rotor good and dist shaft side play good?
Any codes?
Did you disconnect the EST spark timing wire when setting timing?
Is timing mark right?
Some have more than on mark.

What is engine vacuum reading at idle and at 2K rpm?

ironhand33
03-09-2009, 07:04 PM
Things to check.
EGR valve stuck open?
Good Hot blue spark to all plugs.
Good Fuel pressure?
Good compression and ac delco plugs and good plug wires not crossed?
Dist cap and rotor good and dist shaft side play good?
Any codes?
Did you disconnect the EST spark timing wire when setting timing?
Is timing mark right?
Some have more than on mark.

What is engine vacuum reading at idle and at 2K rpm?


EGR brand new
plugs are good
fuel pressure seems to be good... I Just took my timing light shined it on the fuel spray and it appeared to be ok till i pushed on the excellerator. the injector on the passanger side has more of a circle type pattern and the driverside is still a mist.

and what is this i hear about the spark timing wire? how does that work? what is the proper procedure for timing my truck? get the harmonic balancer on TDC then make sure #1 cylander is at TDC then point the roder on the distributor at #1 cylander then un hook the wire or un hook it first in the order?
:eek7: thanx for your input so far.. its helping.

ironhand33
03-09-2009, 07:21 PM
Ok just checked the spray, both sides are circular in spray... I dont know what else to do.. Im at a loss.

ironhand33
03-09-2009, 07:22 PM
EGR brand new
plugs are good
fuel pressure seems to be good... I Just took my timing light shined it on the fuel spray and it appeared to be ok till i pushed on the excellerator. the injector on the passanger side has more of a circle type pattern and the driverside is still a mist.

and what is this i hear about the spark timing wire? how does that work? what is the proper procedure for timing my truck? get the harmonic balancer on TDC then make sure #1 cylander is at TDC then point the roder on the distributor at #1 cylander then un hook the wire or un hook it first in the order?
:eek7: thanx for your input so far.. its helping.


I do have codes, they are map sensor and TPS read low, and O2 sensor lean.. but I have replaced all three.

MT-2500
03-09-2009, 07:38 PM
I do have codes, they are map sensor and TPS read low, and O2 sensor lean.. but I have replaced all three.
Codes do not say to replace.
Clear codes and see if they come back.

To set timing disconnect the est bypass wire.
A single tan wire with a black stripe. with a signal plug in.
May be located on firewall under the triangle black plastic cover or on side of big PCM wiring harness.
And even sometimes over to dist wiring.
Sometimes under glove box or heater housing in cab.
And clear code set after setting time.

MT-2500
03-09-2009, 07:46 PM
Ok just checked the spray, both sides are circular in spray... I dont know what else to do.. Im at a loss.
Proper testing is a good start.
Re Read post no 2 and post back info.

ironhand33
03-09-2009, 07:49 PM
I was told to check the fuel pump... could the faulty fuel pump cause my map sensor, tps sensor, and O2 sensor to code? I was told this could happen because with a fualty fuel pump the truck will run lean... is this so?

rockwood84
03-10-2009, 10:32 AM
put a fuel pressure gauge on the fuel line and see how much pressure the pump is pumping. if the pressure isn't holding over 45+ then the pump will the fuel system sensors will show codes for a lean burn. tps ,o2 sensors ,this is probably causing the backfire,and lack of power when pedal is mash down. the fuel pump is most likely pushing enough to idle[sometimes]but not enough to let the motor run in gear. the fuelpump is doing the backpressuring thing.do you put any injector cleaner in the gas tank? as the tbi's need some once in a while to make them spray correctly.

MT-2500
03-10-2009, 11:38 AM
put a fuel pressure gauge on the fuel line and see how much pressure the pump is pumping. if the pressure isn't holding over 45+ then the pump will the fuel system sensors will show codes for a lean burn. tps ,o2 sensors ,this is probably causing the backfire,and lack of power when pedal is mash down. the fuel pump is most likely pushing enough to idle[sometimes]but not enough to let the motor run in gear. the fuelpump is doing the backpressuring thing.do you put any injector cleaner in the gas tank? as the tbi's need some once in a while to make them spray correctly.

This is a 88 TBI.
Fuel pressure specs are 9/13 lbs.

ironhand33
03-10-2009, 04:20 PM
put a fuel pressure gauge on the fuel line and see how much pressure the pump is pumping. if the pressure isn't holding over 45+ then the pump will the fuel system sensors will show codes for a lean burn. tps ,o2 sensors ,this is probably causing the backfire,and lack of power when pedal is mash down. the fuel pump is most likely pushing enough to idle[sometimes]but not enough to let the motor run in gear. the fuelpump is doing the backpressuring thing.do you put any injector cleaner in the gas tank? as the tbi's need some once in a while to make them spray correctly.


I am gonna try that.. I think my friends dad has a fuel pressure guage I will barrow it from him and check the pressure.. or I may just replace the fuel pump anyway.. lol.... just tired of having to replace crap...

oh check this out.. yesterday i was firing over my truck and my muffler literally exploded... crazy right?:eek7:

j cAT
03-10-2009, 06:37 PM
I am gonna try that.. I think my friends dad has a fuel pressure guage I will barrow it from him and check the pressure.. or I may just replace the fuel pump anyway.. lol.... just tired of having to replace crap...

oh check this out.. yesterday i was firing over my truck and my muffler literally exploded... crazy right?:eek7:

you must check compression, also for excessive exhaust back pressure...

remove the O2 sensor from the exhaust pipe and see if it runs better to check for the exhaust restriction..

don't replace the fuel pump unless you see low fuel pressures..
using a mutimeter measure the plug wire resistances new wires are bad often ..

as mt2500 suggested the distributor may be worn.....if the rotor wobbles too much the spark will not be at the correct time..

GOOD LUCK

rockwood84
03-11-2009, 11:29 PM
i guess i stand corrected.

chevman57
03-12-2009, 09:08 AM
A couple of things to check that i had trouble with on my 1989 chevy pickup that kept having o2 sensor codes is to check the ground wire on the engine. MIne was bolted to the waterneck and had corroded and wasn`t grounding good. Also on the rough idling have you checked the vacuum port that the pcv goes intoin the the front of the TBI to see if it is not clogged with carbon buildup? And check the TBI base gasket too.
Terry

jrhageman
05-02-2013, 09:30 PM
I need to know if you ever fixed your truck?? exactly same problem and tried all the same fixes but now I'm stuck and you never came back and said if you fixed it or not and how????

MT-2500
05-03-2013, 09:33 AM
I need to know if you ever fixed your truck?? exactly same problem and tried all the same fixes but now I'm stuck and you never came back and said if you fixed it or not and how????
Welcome to AF
This post is over 3 years old!!!!!!
If you need help start your Own New Thread.
Give all info and someone will help you.

j cAT
05-03-2013, 06:41 PM
I need to know if you ever fixed your truck?? exactly same problem and tried all the same fixes but now I'm stuck and you never came back and said if you fixed it or not and how????

you have to explain what you did , also what vehicle engine mileage how long you owned it how/what condition , type of use , any modifications engine swaps etc...

ALSO AS MENTIONED START YOUR OWN POST. this will get better results. good luck !

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