1995 k1500 350 very rough idle

[Lt1roady445]

Well I recently had this truck given to me by a family member. The truck has always had somewhat of a surge at low rpm. Never could find any vacuum leak. Had an ICM leave me stranded on the side of the road and replaced it. The truck would start and ever since this, the truck simply won't run well at all. Fuel pressure reads 18psi (seems kind of high). New ICM, new spark plugs and wires, distributor cap and rotor. Just need a little guidance by someone with more knowledge than me. I've guessed possibly the fuel pressure regulator? Taking spark plugs out tomorrow and seeing if they look rich at all. Can you have high fuel pressure and still not run rich?

 

[Greasemagnet]

Mine did the same thing, it turned out to be the spider injectors and the fuel pressures regulator.

 

[Lt1roady445]

How can you tell if the injectors are bad? They seem like they squirt gas just like they did before. I could be wrong though. Beyond what I could see.

 

[Greasemagnet]

I pulled them out and looked at them and they were covered in crud and sticky, so I replaced them. Truth be told they may have been good but it did fix my idle issue for about a month, then I replaced my fuel pressure regulator and that solved it 100%. That was about 6 years ago.

 

[Gramps]

Mine did the same thing, it turned out to be the spider injectors and the fuel pressures regulator.

With the exception that your truck is a vortec 96+ WITH the spider injectors, and the op is NOT. He has a 95 - tbi injected. Very different animal.

Op 18 psi is very high for a stock tbi engine - first step get a different guage and retest I suspect your guage is reading incorrectly.

Second if the fuel pressure proves to be 11-13psi and there are no “codes” then a scan tool is going to be your friend, you need to see what the ecm is seeing/doing.

 

[RawbDidIt]

Agree with above, borrow a second gage from the local parts store and confirm the high pressure reading. If this high reading is correct, pull the plugs as you said you would and see how it's running. I'm guessing it's actually running lean due to clogged injectors. To my knowledge, fuel pressure regulators usually fail in a way that causes low fuel pressure rather than high. If the injectors are plugged, inspect to find out why. If it's crap on the outside, simply replace and check the air filter, if it's on the inside, you'll want to inspect the lines, tank and fuel filter to ensure it doesn't happen again.

Sent from my SM-N976V using Tapatalk

 

[Schurkey]

Well I recently had this truck given to me by a family member. The truck has always had somewhat of a surge at low rpm. Never could find any vacuum leak. Had an ICM leave me stranded on the side of the road and replaced it. The truck would start and ever since this, the truck simply won't run well at all. Fuel pressure reads 18psi (seems kind of high). New ICM, new spark plugs and wires, distributor cap and rotor. Just need a little guidance by someone with more knowledge than me. I've guessed possibly the fuel pressure regulator? Taking spark plugs out tomorrow and seeing if they look rich at all. Can you have high fuel pressure and still not run rich?

1. Confirm fuel pressure.
2. Scan tool to access data stream and "codes". Especially the data stream!
3. Verify that the ignition system will fire a spark-tester calibrated for HEI ignitions. A failed ignition module may be telling you that the ignition coil is getting weak.

 

[brian5365437]

95 is pre-ODBII (at least mine is). Does ODB still provide steaming data?

 

[Schurkey]

95 is pre-ODBII (at least mine is). Does ODB still provide steaming data?

OBD--On-Board Diagnostics

Yes, sometimes the data you get is a hot, steaming pile of faults and nonsense.

The data stream is almost always available. The first few years of computer-control of engine fuel 'n' spark had some oddballs--the Chevette MIN-T system, and Ford's early system (MCU) I'm not going to vouch for. I've never connected a scan tool to either one. I haven't worked on a Chrysler "Lean Burn" system in decades. I don't think Lean Burn has any data stream; in fact I don't remember fault codes.

Any of the "normal" GM systems from '80 1/2-on-up will provide data stream if your scan tool can communicate with them.

 

[Lt1roady445]

No scanner available. I only have an ob2 reader. Does the paper clip and reference to book work? Accurate info? Somewhat at least?