'87 suburban won't ide in gear?

[Social D]

i have an '87 suburban with a 350 and the FI. it has always run just fine until today. it has been sitting for about 3 to 4 weeks. drove it today and at first it was fine. then it would die at the stop lights and so on. it won't idle in gear. anybody have any helpful hints on the FI? thanks SD

[BIG V]

easy one first fuel filter its cheep and it most likely needs one. then pull the plugs and look at them, if they look bad replace them. let us know how that works

[Social D]

ok i finally got a chance to change the fuel filter. went to start the truck and it would not start at all now. (was going to pull it in my driveway to change filter). r&r filter still would not start. gauge reads 1/4 tank so to make sure gauge is not off i added some gas. still the same. now i can get it to run with starting fluid and will stay running but it wont idle. i do have a factory service manual. been reading it and trying to understand how the fuel system works. just wondering if the TPS or the idle speed sensor could be my problem? probally should plug a scanner in and see if it is giving any codes. thanks SD

[durty harry]

Sounds like fuel filter . with this high octane water now days its best not to let anything sit for any time .

[andyh1956]

on an '87 you don't need a scanner, just jump the correct terms at the diagnostic port. it's a flash code setup. but most likely it won't tell you much. go get a service manual before you start anything. 1st thing after that is to run a fuel pump diagnostic on the fuel system & go from there.
andy

[dropd80s]

I'd guess the fuel pump. Also if you decide it is the pump might drop the tank and check the wire connections in the tank. I had one quit on me. I cleaned the in-tank contacts and she fired right up. The lower quality fuel now days can cuase some corrosion. This causes a lot of sending unit problems too.

[Social D]

ok, i got around to workin, on this thing again. a friend let me use his tps and idle sensor. still no start. i barrowed a fuel system pressure tester, hooked it up. when the key is turned on i have 12 psi for the 2 seconds that the fuel pump turns on till the ecu takes over. but when i crank it the FP is lower. not sure what it should be when it cranks. i would think it would be the same. might drop the tank and check out the fuel pump. thanks

[1LowToy]

Check spark? 12psi don't sound like much for FI but what do I know. I have a Dakota with FI and when she don't idle I pull off the TP sensor and give it the full motion sweep to rub off the contacts and put it back on and its good for another 20k miles.

[Social D]

well it fires on and will run with a shot of starting fluid. so i have spark, i have a manual and it calls for 9 to 13 psi for the tbi. but i am going to check for spark to see if i have something weird going on at crank up. idk

[cr34t3d_by_d4rkd3n]

ur saying fi?..... fuel injection? tpi or tb? tb will run safely from 5-10psi aprox, so 12 on a tb motor is high. tpi thats too weak, i dont know off hand what tpi need but its more than 12......check if its gettn spark, what the plugs are reading, also check oil, low oil pressure will signal a terminate signal to computer and not allow the engine to run.

[rfmaster]

Originally Posted by cr34t3d_by_d4rkd3n

ur saying fi?..... fuel injection? tpi or tb? tb will run safely from 5-10psi aprox, so 12 on a tb motor is high. tpi thats too weak, i dont know off hand what tpi need but its more than 12......check if its gettn spark, what the plugs are reading, also check oil, low oil pressure will signal a terminate signal to computer and not allow the engine to run.

All of the above statements related to TBI are incorrect.

1) GM TBI specified fuel pressure is between 9 and 12 PSI. Generally 15 PSI will make stock engines perform at their best - injectors provide better fuel atomization. Stock engine will idle with 6 psi, but the moment throttles are opened will stall.

2) The oil pressure switch does not 'terminate signal to computer'. Oil pressure switch is used as a fail safe device for a fuel pump relay. If Fuel Pump (FP) relay fails while engine is running the oil pressure switch contacts will provide current to the fuel pump. Oil pressure switches (NO) are designed to close when oil pressure is above 4-6 PSI. If you have bad fuel pump relay it takes a while for engine to start - about 20 to 30 seconds of cranking - oil pressure builds up and closes oil pressure switch contacts energizing fuel pump.

As to original problem - not idling in gear. Perform POST check and pull codes (if any) by jumping pins A&B of ALDL connector - see TBI thread for details. If basic checks are OK it is common on high mileage trucks to build up carbon in the IAC passage ways - this requires TB removal and cleaning. On few rare occasions IAC motor fails - when that happens amount of idle air is not controlled and engine stalls if IAC is fully closed.


//RF

[Social D]

it's a throttle body. i have a factory chevy service manual. it calls for 9 to 13 psi at the fuel filter. most of the trouble shotting in the manual calls for a scanner which i don't have so i have been winging it the best i can.thanks