Jimmy S15 88 Stalling


amtm
08-24-2004, 01:46 PM
I have a jimmy s15 4*4 model 1988 2.8 v6 its been sitting now for about a good 3 or 4 months before it was sitting I never had this problem but now that I'm starting to drive it it constantly stalls I would say it probally stalls about a good 3 or 4 times during a trip and I haven't change anything with it. I was thinking it might have been the fuel filter so when I get underneath the truck where the fuel filter should be the people that had the truck before me basically cut the fuel filter out and did a direct hose no fuel filter anymore I'm not sure if thats causing my problem or not. Another thing that I have notice is when i'm trying to start it it takes me to pump the gas at least 4 to 5 pumps and then try to kick it over at least 2 to 3 times usually it starts on the 2nd try but sometimes it will take 3 times. Know I another strange thing is my check engine light is on and has been on for some time now but what I have notice is when I rev the enigine up to for some reason around 5,000 rpm the light will go off and when it drops it comes back on the oil pressure gauge goes up and down usually thats when it stalls is when it drops to around below 40 psi. What I've done is cleaned out the carberator I put some fuel cleaner in it I've replaced the fuel line. What I'm planning on doing is replacing the oil pressure sensor and maybe adjusting the idling screw put thats what I can think of if anybody has any new things to try please let me know thank you any help would be very appercaited

Teaman3
08-26-2004, 05:06 AM
I have a jimmy s15 4*4 model 1988 2.8 v6 its been sitting now for about a good 3 or 4 months before it was sitting I never had this problem but now that I'm starting to drive it it constantly stalls I would say it probally stalls about a good 3 or 4 times during a trip and I haven't change anything with it. I was thinking it might have been the fuel filter so when I get underneath the truck where the fuel filter should be the people that had the truck before me basically cut the fuel filter out and did a direct hose no fuel filter anymore I'm not sure if thats causing my problem or not. Another thing that I have notice is when i'm trying to start it it takes me to pump the gas at least 4 to 5 pumps and then try to kick it over at least 2 to 3 times usually it starts on the 2nd try but sometimes it will take 3 times. Know I another strange thing is my check engine light is on and has been on for some time now but what I have notice is when I rev the enigine up to for some reason around 5,000 rpm the light will go off and when it drops it comes back on the oil pressure gauge goes up and down usually thats when it stalls is when it drops to around below 40 psi. What I've done is cleaned out the carberator I put some fuel cleaner in it I've replaced the fuel line. What I'm planning on doing is replacing the oil pressure sensor and maybe adjusting the idling screw put thats what I can think of if anybody has any new things to try please let me know thank you any help would be very appercaited

Firstly, revving to 5000 rpm is not a good idea - you'll break something in the engine. Very expensive.

Oil pressure will fluctuate. 40 psi at/near idle is good. If the oil is black, change it and the oil filter.

Adjusting the idle screw may be curing the symptom not the cause. Read on.

You've probably got a mix of problems:

1 Dirt/rust in fuel
2 Clogged drillings in the carb from #1
3 Perished diaphragms
4 Failing ignition module
5 Other fault such as EGR valve stuck partially open, mixture going weak
6 Vapour lock

1 You should fit a fuel filter (www.fram.com (http://www.fram.com)) Walmart's cheap (oil too)

2 & 3 You'll have to strip the carb down to clean it out. Note what bit goes where eg the jets. Haynes or Chilton have good diagrams of the carburettors you can use as reference. Use a penetrating oil eg WD40 to help wash out sludge from the drillings. Then use compressed air to blow out the remainder. WEAR SAFETY GLASSES AND GLOVES. Point the compressed air nozzle AWAY from you at all times so that any particles blown out of the carb drillings fly AWAY. They can have a velocity sufficient to penetrate skin, especially eyes.

Any accelerator pump/vacuum diaphragms should be replaced.

I believe that overhaul kits can be bought so be prepared to buy one, at least for gaskets.

As a last resort you can always buy a replacement carb.

If you can rock the jimmy to slosh the fuel around and then disconnect the fuel line and empty some fuel into a large clean container (fuel can). Let the fuel stand for 24 hours. If you can then see a definite smear of brown sediment settled on the bottom you'll likely have to remove the tank and clean it out. Leave this t'ill last when all else fails.

You should also check all the vacuum lines. Replace cracked tubing and seal joints. There are a couple of spigots on the intake throat that are the wrong type for vacuum pipe. Use a coarse grade oxide paper to roughen the surfaces. Hylomar gasket compound makes a good vacuum joint sealer.

The Jimmy very likely, will run weak. Check your ECM Error Codes, they'll point you to a problem.

When warmed up, it sucks a load of air via the charcoal canister, air pump control valve and the EGR valve vacuum switch. I've fitted restrictors to the air pump and canister lines. The EGR vacuum switch I changed to another later type, from a scrap yard GM vehicle, that positively shuts off ( the original type don't, they leak a lot ). To the hot air intake valve vacuum line I fitted a temperature driven shut off valve. Same idea as the charcoal canister valve, in reverse. Scrapyard visit.

5 Remove and clean the EGR valve seat, checking the valve for correct operation too.

You should also change the cooling system thermostat and clean out the cooling system at the same time.

If the computer decides the engine is too hot it will open the EGR valve. A sticky EGR valve can cause engine stall. So avoid overheating and clean the valve.

6 Too hot an engine will also cause vapour lock. This is where the fuel in the carburettor gets vaporised before it should. So instead of a liquid fuel arriving at a jet, a vapour does, causing the mixture to drastically weaken = stall.

A hot engine can sometimes cause vapour lock in a fuel pump, but this rare, so leave t'ill last

Checking the temperature senders for accuracy is a good idea.

IGNITION

4 The Ignition Module is mounted on the distributor. Where it is is not a good place for electronics too ruddy hot ! So they fail and usually slowly, a bit more each time they get cooked.

To replace it entails removing the distributor, so if you haven't bought a Haynes or Chilton manual yet, go get one. They'll tell you how to remove the dizzy, what words you use in the process is up to you. Whatever you say, you'll either need a 1/4" drive 1/2" socket on 6" to 8" of wobble bar with a UJ coupling at the end OR a special cranked spanner at some horrendous price. Your choice. BUT be careful not to drop anything down the back as it's an absolute "@#*ing pain to retrieve it !

Before you remove the distributor, clean the base of it of grit, grease etc. Muck down the distributor hole is not a good idea. BEWARE when removing the distributor, there is a hexagonal rod loosely attached to the bottom end of it. It might NOT disengage and will come out with the dizzy. Shake the dizzy as you SLOWLY pull it out VERTICALLY as possible to make the rod drop off.

Your distributor may be the mechanical advance/retard type; vacuum and/or weights. Check vacuum A/R for perished diaphragm and weights for freedom of movement/sticking (5000 rpm....)

If your Jimmy has the sound deadening material fitted to the bonnet/hood, it's likely it drops onto the air pan when the bonnet/hood is down. Making a gap between it and the top of the air pan is helpful for the module and carburettor by allowing air to flow more over the top of the engine to the back.


You should also check the chassis ground for the Oxy sensor (if fitted) in the exhaust. There probably isn't any, hence the ECM will read a value that appears to be "mixture rich" and will lean the mixture. A hose clamp and some 14 gauge wire will restore the ground. Attach the wire to the clamp (use slotted band stainless steel type) by weaving the (lightly greased) conductor in and out some of the slots. Clamp on sensor (if old sensor, fit a new one; they don't last forever) and run other end to chassis ground avoiding the exhaust pipe.

If the vehicle has been standing for some time, you should ensure the brakes aren't binding (rust/dirt). Binding brakes will help make the engine overheat and use more fuel than normal.

Well that should keep you busy http://www.automotiveforums.com/vbulletin/images/smilies/smile.gif


Teaman3

amtm
08-26-2004, 08:09 PM
Teaman3 let me start off by saying thanks for giving me all the info and replying to my thread I just want to let you know I found out what the problem was I checked my spark plug and it looked like kind of black around the tips it seems like it was flooding out so i checked my engine out and the problem was the idle control air valve 27.99 auto parts everything is good now thank you for the advice l8ter

Teaman3
08-26-2004, 11:46 PM
That'll do it too.http://www.automotiveforums.com/vbulletin/images/icons/icon7.gif Glad you've found and sorted the problem.

Still inspect your vacuum lines though. Mine's an 88 and my latest is the vacuum feed to the interior ventilation vacuum motors; fractured where it passes through the bulkhead. Leaky lines means loss of power. I'm gaining a few degrees of advance = power for the same amount of fuel by having gas tight lines.


Have fun http://www.automotiveforums.com/vbulletin/images/smilies/tongue.gif

amtm
08-28-2004, 04:53 PM
Man I can believe it Everything was working fine and now all of a sudden it starts to stall again I was thinking of replacing the oxygen sensor do you think that might fix the problem

Teaman3
08-28-2004, 05:56 PM
The oxy sensor is only taken notice of after a preset period of time to allow it to warm up and produce a non-erratic output. Having said that, if it's old there's no harm in replacing it, just the dent in your wallet ! With the oxy sensor, I've found that there's usually a poor or no chassis ground through the exhaust system. Rust is not a good conductor of electricity. As with all the other sensors there HAS to be a 100% chassis ground, otherwise the sensor signal will be false. The fix is to attach some wire to the sensor casing which is usually part of the ground side of it. 14 gauge is fine. Strip back an inch of conductor and thread it through a few slots on a stainless steel hose clip. Put a fine coating of grease on the conductor to prevent it oxidising. Fit the clip/wire to the oxy sensor casing. Route the wire clear of the exhaust, into the engine bay and attach either to the (cleaned) ground point above the blower motor, or direct to the battery.

The rule of thumb in fault finding is to start with the simple and obvious things.

EG

Loose connectors
Oxidised connectors
Loose vac lines
Components loose and/or broken

Get yourself a beer/coffee/coke and just steadily look over the engine, taking your time. You'll see things more clearly eg wire burnt, line pinched, belt loose/tight, leaks, hose rubbing.

A common faults I've seen:

EGR valve sticking slightly open
IAC valve not resetting properly or failing. Reset: Ignition ONLY on 5 seconds, OFF, start/run engine 10 seconds.

If the air injector system is connected to pump air into the INLET manifold, any valves/relays should checked.

Then you go on to examine the sensors. Sensors that are heated will become inaccurate eventually. The degree of inaccuracy may still be acceptable. This is where original data is needed for comparision. So if it looks ancient replace it.

Going back to connectors, I would advise you to go round them, including the ECM ones (very important), and the battery. Clean if necessary, and finely coat with some petroleum jelly using a fine tip paint brush. There's usually a noticeable improvement in performance stability. As an aside, if you do this on the lights, bulbs (casings), earth points and connectors, your lights stay bright for ages, saving you some time and money.

Tip: Carry a spare ignition module. When they fail your dead in the water.


:o)

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