Sudden Power Loss

[Traakon]

Hey Y'all-

Yea, I have not been around here much but to read threads because the 'cruizer has been running well and I don't have any current projects planned for it while its "Saudi Hot" here. Just building the parts shelf for full bushing replacement, lift, and cooling system replacement when things temper down. (Got the new radiator from Mr. T last week)

Yesterday, while riding the 202 the 'cruizer suddenly nosed over like I had hit the brakes, dropped power and then went into what I would modernly call "Limp Mode". No indication of what was happening from the gauges so I eased it toward the shoulder/offramp at the limp pace of 35mph. just as i reached the ramp it woke up once more and seemed fine.

I pulled into the parking lot and did a walk around...saw nothing. Nothing under the hood seemed amiss and when I got home the only code flashing was the EGR code it has had from day one with us that I have never been able to get cleared for more than a couple days.

Any thoughts on where to stick my nose next on this?

 

[Traakon]

OK, for weeks I have been chasing this as a "fuel" issue but it is so random and intermittent I am wondering if I have an electrical or ignition issue.
Any thoughts where I can begin exploring this side of the equation without random parts replacement?

 

[baldilocks]

Don't want to leave you hanging like you have been since mid July but I have never had this exact issue and can't tell you where to begin.
When it falls on its face, it continues to run smoothly but with very little power? Unusual odors or noises? Evidence out the tail pipe? What have you done so far exactly? Do you have an FSM?

 

[jfz80]

Possibly a knock sensor going out ?

I had similar experience and that was the culprit but it threw a code

Another thought would be throttle position sensor. That has been known to give issues without a code. There's an fsm test for this one

*** this applies to 95. Not sure about 93. Im thinking yours is different

Possibly a fault in the circuit opening relay or assoc circuit is a possibility. Doubtful and im not much help here even though im battling an issue here. I believe Maf and dizzy are in the same circuit. The relay is in USDS kick panel and same as efi main.

 

[Traakon]

Don't want to leave you hanging like you have been since mid July but I have never had this exact issue and can't tell you where to begin.
When it falls on its face, it continues to run smoothly but with very little power? Unusual odors or noises? Evidence out the tail pipe? What have you done so far exactly? Do you have an FSM?

The issue is a real puzzle and yes on the FSM which has nothing in it to address this.
No smells, drips, leaks or other telltales to give away the issue.
My initial thought was the trans so I went through it and found nothing. Then I considered bad fuel so I have been through the fuel system from tank to front and found nothing. That has left me with wondering if it is electrical but where to start.
Still the only CEL I have is for the EGR.

 

[Traakon]

Possibly a knock sensor going out ?

I had similar experience and that was the culprit but it threw a code

Another thought would be throttle position sensor. That has been known to give issues without a code. There's an fsm test for this one

*** this applies to 95. Not sure about 93. Im thinking yours is different

Possibly a fault in the circuit opening relay or assoc circuit is a possibility. Doubtful and im not much help here even though im battling an issue here. I believe Maf and dizzy are in the same circuit. The relay is in USDS kick panel and same as efi main.

The '93 doesn't use the MAF it has the AFM which is new since I acquired the 'Cruiser as the old one had a bad air temp sensor.

 

[baldilocks]

Sounds like you have the ability to handle this issue, it will just take patients to test every component per the FSM, inspect the harness and look for shorts test for shorts. I look forward to following your progress.
I don't know what month your 80 was built but some or possibly all 1993 models had a known issue with the engine ECU. Perhaps you could find a member who lives near you that owns a 93/94 who would let you slave their ECU in. I know, the problem is intermittent so maybe just buy one. They can be had for around $100.

 

[ZackR]

I think there was a recent thread on this that alluded to a knock sensor going out. Check the codes and report back.

 

[Traakon]

One of the things I have on the "To Do" list is new battery cables and fuseable link. I have read where they can cause some really odd issues with ignition and intermittents.
I have had all the "fixins" on the shelf but the links for a couple months but time is always the hiccup for me. That's why I have come to the brain trust, if I had unending time I could just pick at it for days but I only have a few hours at a time.

 

[Traakon]

I think there was a recent thread on this that alluded to a knock sensor going out. Check the codes and report back.

Only code is the "71" for the EGR which I have had since I bought the 'Cruiser. Been chasing it a little at a time as well; new vacuum lines, EGR valve and modulator, temp sensor wiring inspection and yet it still remains. I need to pull the intake i think but just have not had time.

 

[Traakon]

Well this issue seems to not want to be resolved.
Chased it down the "control system" route and replaced the ECM and that removed the EGR code but the power loss remained.

Looked at the fuel delivery side since the engine did not die, just acted like it was out of gas and no CEL activations. New fuel pump, fuel pump relay, fuel pump resistor. No change and if anything it got worse going from the occasional occurrence to every time it is driven.

Did a charcoal canister replacement (use the mod to the GM unit) and damned if the thing didn't throw new codes on the test drive...31 and 71...the EGR code returns after 3 weeks away. The falter is worse than ever.

I ordered a new coil from Mr. T and will look at the ignition side of the symptom there since the cap, rotor, plugs and wires are all new but I did not replace the coil when I did those.

On the upside, I am setting a baseline for lots of new parts and Larry and Tom know me by name, just wish something would actually resolve the problems.

 

[Masud]

Well this issue seems to not want to be resolved.
Chased it down the "control system" route and replaced the ECM and that removed the EGR code but the power loss remained.

Looked at the fuel delivery side since the engine did not die, just acted like it was out of gas and no CEL activations. New fuel pump, fuel pump relay, fuel pump resistor. No change and if anything it got worse going from the occasional occurrence to every time it is driven.

Did a charcoal canister replacement (use the mod to the GM unit) and damned if the thing didn't throw new codes on the test drive...31 and 71...the EGR code returns after 3 weeks away. The falter is worse than ever.

I ordered a new coil from Mr. T and will look at the ignition side of the symptom there since the cap, rotor, plugs and wires are all new but I did not replace the coil when I did those.

On the upside, I am setting a baseline for lots of new parts and Larry and Tom know me by name, just wish something would actually resolve the problems.

I'm facing a similar issue I had a thread up about how my car goes into limp mode and after couple of minute of limp driving it runs fine once again. I replaced my knock sensor and it did not resolve my problem. Next up it's time to change my throttle position sensor and the VAF(both parts ordered and on the way) I hope these two things fix the problem because I'm looking forward to hit Lake Tahoe this year

 

[Traakon]

I replaced the AFM shortly after we bought the 'Cruiser due to an intake air temp code. It has had the EGR code forever but for the 2+ weeks just after the new ECM and right before the new vapor canister.
I have thought about the TPS because when it does act up if you shift the peddle position there are places where it seems like it wants to come out of the condition and then slides past.
It's pretty frustrating. The 'Cruiser is the wife's daily and she is becoming afraid to drive it and I am running out of directions to investigate and parts to replace.

 

[Masud]

I replaced the AFM shortly after we bought the 'Cruiser due to an intake air temp code. It has had the EGR code forever but for the 2+ weeks just after the new ECM and right before the new vapor canister.
I have thought about the TPS because when it does act up if you shift the peddle position there are places where it seems like it wants to come out of the condition and then slides past.
It's pretty frustrating. The 'Cruiser is the wife's daily and she is becoming afraid to drive it and I am running out of directions to investigate and parts to replace.

Yea I know the frustration mines been in garage for a good month now problems pop up left and right and parts are expensive

 

[Traakon]

I always expect to spend a lot of time wrenching things when buying one of my wife's "Oh I have wanted one of those forever" vehicles.

Usually its pretty straight forward but this issue (and the EGR code) have been very frustrating.

In the beginning I teased my wife that she was crazy, it would act up on her but I could drive it for a couple hours and nothing. She continued to complain and I even got my buddy, a 40 year GM master mechanic to test drive it with me...not a hiccup.

Finally it acted up on me and it felt like it was not getting fuel. I really did not initially go to the fuel pump because the PO said it had been replaced (not true) so I started chasing electrical issues related to the fuel system control. Relay, resistor, even the ECM. Finally pulled the interior and did the fuel pump. With every step it actually made the problem more evident/worse.

I'm going to replace the coil, the last part of the ignition side I have not replaced since buying and then perhaps/probably the TPS.

Based on the fact that I still have an EGR code I may even order a new engine wiring harness on the chance that I have multiple issues in the wiring. At $400.00+ I don't want to bite that apple until i have run out of options.

 

[SmokingRocks]

I hate to say it because everyone seaminly does... but did you check the wiring harness around the egr for melts? Are your injectors all plugged in and not melted?

 

[Traakon]

I hate to say it because everyone seaminly does... but did you check the wiring harness around the egr for melts? Are your injectors all plugged in and not melted?

You're right, everyone does go there the minute you mention the EGR 71 code.
No visually crispy wiring.

At some point I suspect I will have to pull the entire intake and at that point there are a lot of things that will get replaced i.e. injectors, pressure reg etc. But as this is the wife's DD I can't have it down for more than a Sunday right now unless there is no choice.

 

[bicycleagent003]

Air/fuel ratio (upstream) oxygen sensor is a culprit, in my opinion.

 

[balcc9481]

Air/fuel ratio (upstream) oxygen sensor is a culprit, in my opinion.

Forgive my ignorance, but do you mean the sensors on the exhaust system?

 

[inkpot]

Have seen this happen intermittently due to loose/broken/frayed wire-connector on knock sensor.