93 Suburban dies when running idle and is hard to start

My suburban will not run when idle. It occasionally starts and will run for a little bit, but then cuts off. I have checked the sensors, and they all seem to be in good shape. The fuel pump cuts on when I turn the key, and I can hear fuel getting to the back of the throttle body. I have replaced the fuel filter, but that didn't fix the problem. The injectors appear to be getting the signal to fire because when hooked up to a multimeter, I get 12V running through. Could the problem be with the fuel pressure regulator or is it electrical? Any other suggestions for tests I could run? Thanks, Brett

How does the spark look???

IS there any? Cap rotor look OK, plug wires, plugs all in good condition?

Check spark at plugs (use plug wire pliers so you dont get zapped). Check fuel pressure using a gage, it should be at 42. Have you scanned it yet? See if there are any codes coming up, post it here and maybe I can help.

Good idea to check fuel pressure, I'm still thinking spark on first pass. If it is not, and fuel pressure is good, could be TB injectors. I did end up replacing mine at around 100K as I recall and it had similar symptoms.


Oh yeah, and in addition to my Suburban, I also have TWO jeeps... :iceslolan ....nice....

Nothing but SUVs here at the Eagle Roost.

Yeah, it could be the TB injectors also. Good call. :)

I have a 99 Cherokee, but it is the family vehicle, so it is done mildly. It has a Rusty's 4.5 lift and some 33's with beadlocks. My wife wont let me trail it though, because it is hers. :banghead:

The next step I plan on trying is looking at the fuel pressure and trouble codes. I have a gauge but it doesn't seem to work correctly. It's kind of old. A new one is about $40 at Sears. I'm pretty sure it's getting spark because the plugs were replaced not too long ago, but I'll check that if the other tests turn out ok. I think I forgot to mention that when I try to crank the engine fuel only comes out of the injectors once every third try or so. That's why I'm thinking it's something wrong with the fuel and not the spark. Thanks, Brett

The next step I plan on trying is looking at the fuel pressure and trouble codes. I have a gauge but it doesn't seem to work correctly. It's kind of old. A new one is about $40 at Sears. I'm pretty sure it's getting spark because the plugs were replaced not too long ago, but I'll check that if the other tests turn out ok. I think I forgot to mention that when I try to crank the engine fuel only comes out of the injectors once every third try or so. That's why I'm thinking it's something wrong with the fuel and not the spark. Thanks, Brett
OK now that you mention that info, I think you are right. Now I am betting on the injectors...

Yeah, it could be the TB injectors also. Good call. :)

I have a 99 Cherokee, but it is the family vehicle, so it is done mildly. It has a Rusty's 4.5 lift and some 33's with beadlocks. My wife wont let me trail it though, because it is hers. :banghead:

Yeah, I have a 00 Wrangler Sahara with a 4-1/2" Lift 33" x12.5 tires...nothing radical...just nice looking. I have had it up to the Rubicon, but it is not really set up to rock crawl.
The wifes car is an 00 Grand Cherokee with the V-8. I have done nothing but Rancho shocks on it, and she hates them. She is not so into the boy toy thing....

Well, I bought an Acton III fuel pressure tester today, so as soon as it warms up a little, I'll check the fuel pressure and let you guys know what's up. In the mean time I guess I can go ahead and check the trouble codes. More tomorrow... Brett

Oh yeah! Has any one every heard of a NOID kit and where I might be able to find one? It's basically something you plug in series with your fuel injectors, and it lights up when an electric pulse goes through.

Oh yeah! Has any one every heard of a NOID kit and where I might be able to find one? It's basically something you plug in series with your fuel injectors, and it lights up when an electric pulse goes through.


Give this a try:

NOID (http://www.otctools.com/newcatalog/detail.php3?id=310)

Better still:

Northern Noid (http://www.northerntool.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=4006970&storeId=6970&langId=-1&productId=299003&cm_tl=auto&cm_partner=tl)

OK, so I finally have an update on the situation. No trouble codes are appearing, and the fuel pressure is a constant 13 psi while the engine cranks or is running. If the suburban starts it will continue to run as long as the rpms are kept above 1000. I plan on ordering a NOID kit sometime soon to see if the injectors are getting the signal to fire. This is getting pretty crazy. More to come soon... Brett

Well, I got the NOID kit at O'reilly's auto parts and put it on the burb. When I cranked the engine, it didn't light up, indicating that no signal is getting to the injectors. By chance, it started up, and as I kept it above 100 rpms, the light was on, but when I took my foot off the accelerator, it died and the light went off. So now what should I do?

Ahhhhh!!!! This is driving me crazy! The wiring harness, injector solenoids, fuses, relays, you name it all appear to be in working condition. Why isn't this thing working? I am almost convinced the ECM is bad, but no trouble codes appear. Does anyone know why an ECM would fail to give the injectors a signal to fire when cranking or running idle and provide a signal to the injectors when I keep the rpms up? Is it failing? Please, any help would be greatly appreciated! Brett

Did you find out what the problem was with your burb. I'm having similar problems.

Is this an ALDL system? If so, are you getting a code 12?
Start with the basics. Have you checked your vacuum lines, especially to the MAP sensor. Have you checked to see if your ECM fuses ('91 has two, not sure about your's) and/or crank fuse is good. It appears to be TBI from your post. Check to see if your wires to your injectors are grounding at the air filter housing). Check your ECM grounds (on '91 @ intake, thermostat housing RH bolt. What's the IAC count when you turn on your key?

Sorry I never posted the solution. It turns out the ignition module was faulty. I took it in to O'Reilly's and they tested it for me. It only occasionally failed, but as soon as it was replaced, the suburban ran fine.