Red1990VT

The attached file is from a long drive in my 1982 Collector's Edition. I love this car, but it has and continues to be a hair pulling experience. The Crossfire system throws no codes, and idles very smoothly. But, try to go up a hill, and it stumbles and even dies if the accelerator is not feathered.

Throttle bodies are balanced. Thermostat is 195 degrees. TPS is properly set, with Idle at 475RPM in drive per the FSM, then idle readjusted per FSM once TPS is set at .525. Coolant Sensor working. IAC motors functioning, idle drops to 650 or less in Drive and again is quite smooth. I've tried looking for vacuum leaks by eliminating all sources of vacuum. No change. Timing is 6 degrees BTDC with the timing lead disconnected. Timing advances when the lead is reconnected. Fuel pressure (upgraded pump last June) is 13 PSI under all conditions. In short, everything seems to be nominal and within factory spec.

But no matter what I do, the car stumbles going up a hill. Feels like missing, sputtering, and silence. Car cuts out and will die unless I let off the throttle and feather it. Then it comes back, and bucks terribly.

Going on level ground the car can fly. No problem burying the speedometer on the highway. But, start up a hill, it stumbles.

I've attached a lengthy WINALDL file in an Excel format. I'd appreciate any help anyone can offer. One problem I do see is that the TBI system seems to have a One set in the Asynchronous Pulse column, meaning the system thinks it needs to be in Acceleration Enrichment all the time, even while in Closed Loop. Not sure I understand this, but it may indicate a problem since the fuel injectors should be alternately fired by the ECM.

Again, any help appreciated.

Red1990VT

Oh, and the EGR system is functioning properly too

terry82

did this happen before you changed the fuel pump ?how much gas is in the fuel tank?I would check for a fuel leak from the fuel pump to the rubber fuel line .I have heard of 82s sputtering when they go around corners and the fuel is low .Fill up the tank and see what happens.

7T1vette

Your car has a 700R4 overdrive transmission with a lockup clutch. It is possible that the system which causes the lockup clutch to drop out (when too much drive torque is applied) has failed and your engine is just bogging down. I believe that there is a vacuum level sensor somewhere in or around the transmission that signals lockup (via the ECM) to drop off under significant accelerator application. Could be that sensor is bad.

Check into that system via the Shop Manual for your year.

Red1990VT

Thanks for your reply. The car was actually much worse with the old pump, which I think was the original from the factory. The car has a little over 100K on the odometer, which judging from the history I got with the car, and the dry rotted Goodyear Polysteel tires I had to replace, mileage seem accurate and correct.

Fuel pressure is a steady 13 psi under all load conditions, and I've filled it with the highest octane (93) available in my area. Unfortunately the car still bogs down under load...

Red1990VT

Thanks for your reply, I will check that. One thing I've noticed is that the car shift into the highest gear very early (27mph) and I've chalked that up to early 1980s GM attempts to get fuel economy up. Maybe it's more of a problem than I've been giving it credit for. Going up a hill I often grab the console shift lever and drop the car from D to 3, revs climb, and it helps, however the car still bucks and dies if I do not feather the throttle. I often end up crawling up hills even in 3 instead of D, and luckily no one has been tailgating me.

I have noticed manifold Vacuum is just at the boundary of red and green on my gauge - 18 inches, steady idle in drive, gauge says late ignition timing. I advanced static timing from 6 to 8 but no change on gauge. This was done with my vacuum gauge connected to the thermac port on the rear throttle body (steady unswitched manifold vacuum). I am going to do some of the diagnostics I've found on line for marginal vacuum and post those. Interestingly enough the sites I've consulted all reminded the reader that vacuum problems can show up as transmission issues, since shifting is based at least in part on vacuum.

I did notice the MAP sensor readings (which are after all just the manifold vacuum) don't appear strange or funny in the WINALDL log file. But the 18 inches at idle is not right and might be the Big Clue here.


Thanks again for your reply. As soon as I do the diagnostics for vacuum I will post them, and consult the FSM for what you suggested regarding the lockup clutch sensor and lockup behavior.

terry82

if the car is better with the new pump ,its sounds like fuel related.how are you checking fuel pressure?http://crossfireinjection.net/catalog.htm

lionelhutz

It seems the BLM is well above 128 for all throttle positions which is indicative that it's not getting enough fuel. I don't see anything specific that would indicate an exact problem though.

I believe the ECM controls the TCC. At least the log shows a TCC on and off flag. The transmission shifting is controlled by the TV cable so make sure it's correctly adjusted. Not only will the shifts be off but you can burn-up the transmission if it's adjusted wrong.

74 LS4-454

this is what I would try as something similar happened to me last year as my 82 would not go above 3000 r's on flat roads let alone hills. I changed the fuel filter and it solved that problem. I now have 130,000 miles plus and it always ran great with that one exception....have you also check your ignition system, including the ignition module??? hope you get it corrected.....

Red1990VT

I'm checking fuel pressure by T-ing into the line between the two throttle bodies. The metal line is long gone, and I bent some tubing to replace it, but had to put high pressure hose in too, as I could not get all the complex bends to line up just right. That in turn makes it easy to T into that fuel line. I then tape the gas pressure gauge to the windshield where I can monitor it while driving, stays at 13psi.

I replace the fuel filter some time back and it did not change things. Probably coming due again tho.

And I will double check the transmission cable, it could be misadjusted, however the car seem to shift ok, just early into overdrive. Maybe too early...thanks for the thought, I will check. I know vacuum problems can also affect shifts, and also haven't yet ruled out a vacuum issue.

I do wonder about ignition issues, and the distributor mounted module, which may be the original. Outboard EST module seem to be ok, at least no codes, and idle is smooth. However the FSM notes that idle can be fine but marginal plugs will misfire at higher RPMs. Pulled plugs one and seven and both looked great, no carbon, just a clean light chocolate color. I replaced plugs cap rotor and wires when i got the car, but no change. There could still be an ignition issue tho, haven't ruled that out.

lionelhutz

Vacuum is not used to control shifting on a 700R4.

Drawmain

I was having a similar problem. I replaced the injectors and the problem went away.

Red1990VT

Not directly, but if the vacuum is incorrect I would think the ECM control of overdrive would be messed up...but that is one area I really need to do more learning...thanks

Red1990VT

I've been wishing I had a way to look at the injectors while the problem is occurring. The fuel spray cones are nice at idle, and there is no leakage with fuel pressure applied and the engine off. But I have no way of knowing what the injectors are doing when the problem is occurring under load. If nothing else works, I'm thinking of sending the fuel injectors off for flow testing and possible replacement.

One thing I did check was the part numbers of the injectors and the front and rear locations, and they were correct.

Thanks, I may yet have an injector replacement in my future...

74 LS4-454

It wouldn't hurt to change out the fuel filter again, as there could be some dirt still in the tank or lines. and take the ignition module out and have it checked by your local parts store.....just make sure that there is a coating of thermal compound between the bottom of the module and the plate on which it is attached, otherwise you may be overheating the module which may cause issues as you are bringing the r's up......just a thought!!!!

lionelhutz

Once again, vacuum is not used to control shifting on a 700R4. Not even overdrive.

The early GM fuel injection converter lockup strategy used throttle position vs road speed.

Besides, the lower vacuum would delay the shift points or converter lockup if the transmission was controlled via vacuum.

terry82

the shifting in to overdrive early is a normal problem on 82s.That can be changed with a aftermarket prom.i would use a timing light on the injectors and see how they look .may not tell you much because it is not under load, but something to try .

Red1990VT

Thanks to all who have offered help and thoughts recently, especially the update on how the transmission is controlled by the throttle position only for overdrive...I've been away for a few days but got back to this today and (re)did a vacuum gauge test...

The car today (cool humid day) has a nice steady 20 inches of Hg at idle today, warmed up and in neutral or Park. Put it in drive and the vacuum drops to about 17, and fluctuates slowly about from about 16.5 to 17.5. Changing the timing, lead disconnected of course, even radically advancing it, does not change this. So, late timing does not seem to be the culprit.

Putting the car either in drive or neutral and 'blipping' the throttle drops the vacuum to zero, and it goes quickly up to about 25, and then settles back at 20 in neutral or 17ish in drive. Again, the vacuum wanders around 16.5 to 17.5 in drive. The needle does not fluctuate rapidly, it just wanders. Once in a while blipping results in the needle going all the way back to 15 and then moving around before settling back around 17. But in drive and after the car settles back down, it is 16.5 to 17.5 and slowly back and forth.

So, I'm thinking from all the research I've done on using a vacuum gauge to check engine health, this just might be an ignition problem after all.

A new fuel filter is probably prudent, and testing the ignition module too. I may take it a step further and replace the cap, rotor, plugs and wires too, as those things have been on the car since I changed them when I purchased it several year ago.

I may also still flow test the injectors, but injectors don't seem to figure in to a low but steady vacuum...I'm not sure how soon I'll get to the ignition system but I'll let everyone know how it turns out.

74 LS4-454

Glad you are getting things sorted out, again to repeat myself, just make sure that when you reinstall the ignition module to use the thermal compound or equivalent on the bottom of the module, otherwise you will eventually fry the module which will cause you more problems than you would like.....
Looking forward to your results...........Tom

cardo0

Looked over your file. What i see whenever TPS increases enough (throttle position opens) to make MAP reading go up (> 200) as expected and it seems to go lean on the O2 (lines 86, 87, 90, 91, 117, 158, 166) when rpm is <2000. BLM dont change but maybe dont have time to react. Now lines 305, 306, 345, 372 are a little backwards of this but maybe due to transient condition.

At over 2000rpm lines 473 through 484 show the O2 nearly maxed out (>900mV). Again at lines 502 - 506.

Lines 552, 576 O2 is low again but low rpm (1525) again also.

Im think'n u have a rich condition above 2000rpm boss man.

BTW i didnt read u have replaced the O2 sensor yet. Most owners arent aware the O2 is a normal wear item. FYI tuners will tell u to replace O2s every time u replace the tires or brakes.

Dont really know what would make it richer at higher rpm and loads other than maybe injectors are larger than stock or fuel press was increased.

My advice is u need a new fuel map.

Hope this helps and good luck.