a couple times in the last week or so my 91 deville has stuttered when accelerating onto the highway. It does it around 50 mph or so. Basically the car stops accelerating and feels like I put on the brake for about a second or two, then continues like nothign ever happened. The error codes I received are E60,E70, and E91. The intermittent TPS code comes on regularly. IF I clear it, it usually comes back after 2-3 days. I've purchased multiple tps switches and replaced wiring. Didn't seem to fix, but I don't think that's what the problem is (its been like that for the last few years and never done this). EGR is not clogged. Any ideas?

Also this engine has been tuned up (new everything) back in february.

I'm going through similar experience my self with my 92 sdv.,I think I have it down to weak fuel pump (through advice on this forum),I'm taking it to mechanic tomorrow for pressure test on pump,will let you know,
How does your car start for the first start of the day?.
Look for current threads and posts on this page for my comments, creeker.

Car starts up strong. I'm not too sure of the weak fuel pump. I put a new one in 3 years ago. Today on the way home from my lunch break the car did it at 76 mph on cruise shortly after getting on the highway. I cleared the codes and it was fine on the way back to work. No codes now after that 10 min drive.

Car starts up strong. I'm not too sure of the weak fuel pump. I put a new one in 3 years ago. Today on the way home from my lunch break the car did it at 76 mph on cruise shortly after getting on the highway. I cleared the codes and it was fine on the way back to work. No codes now after that 10 min drive.

I'm curious, when you clear the codes does it also solve the problem for awhile?,
The more I learn trying to solve my problem the more confusing it gets,theres a lot of things it could be, lots of sensors for one thing,
The MAP sensor for one I think regulates fuel flow,I really dont know if
that is your problem,thats why I'm taking mine in for some tests,rather then
buying a bunch of stuff that may not even work
Also,theres an explanation of the codes on top of this forum.

Car starts up strong. I'm not too sure of the weak fuel pump. I put a new one in 3 years ago. Today on the way home from my lunch break the car did it at 76 mph on cruise shortly after getting on the highway. I cleared the codes and it was fine on the way back to work. No codes now after that 10 min drive.

Forgot to ask you,did you actually put in the fuel pump yourself?, I'm thinking of tackling the job myself if it's a faulty fuel pump.

Yes, i replaced it. Its a pain in the ass IMO. Might be one to have a shop do. I'll have to do it again soon though because I want to powdercoat my gas tank. The problem is very intermittent so I can't really describe when it does it, only that it does it at speeds >45 mph. Then again because of teh wire wheels my speedo is 10% off. I'm wondering if its related to the cruise control and transmission based on those codes. Maybe I'll replace the prndl switch and see if it works. The transmission is the only thing I have not replaced or modified on this car...

I know this is gonna sound too simple, but I've had spark plugs that acted up under acceleration and high speed driving. Seems like high cylinder pressures during acceleration and high speed driving were affecting a plug.

Yes, i replaced it. Its a pain in the ass IMO. Might be one to have a shop do. I'll have to do it again soon though because I want to powdercoat my gas tank. The problem is very intermittent so I can't really describe when it does it, only that it does it at speeds >45 mph. Then again because of teh wire wheels my speedo is 10% off. I'm wondering if its related to the cruise control and transmission based on those codes. Maybe I'll replace the prndl switch and see if it works. The transmission is the only thing I have not replaced or modified on this car...

I guess your at the point of no return,you have put so much money into
it at this point that you cant afford to quit now.good luck.

I know this is gonna sound too simple, but I've had spark plugs that acted up under acceleration and high speed driving. Seems like high cylinder pressures during acceleration and high speed driving were affecting a plug.

Hey, any input is welcome,I tend to overlook the obvious, cant see the forest for the trees sorta thing.

could be. BUt it is strange that it only does it at high speeds. It might only be doing it in cruise too. I'll have to give it a little more and see.

Why not throw the oem wheels back on and see if there's any improvement? 10% is a large size difference and will be more apparent to the trans at high speeds.

How about another long shot:confused:
Many years back I had a similar problem, can't remember which car, but when the engine moved around from torque etc, some wiring was rubbing to ground, driving me crazy before finding the problem. On a similar note, last spring my S-10 4X4 pickup had a problem which turned out to be a loose wire hanging down under the truck, occasionally rubbing on the front drive shaft. It rubbed enough to take out the ECM before I found it.
All kinds of weird things happen to cars it seems.

I don't have the oem wheels anymore.

It hasn't done it since mid day yesterday. On my break yesterday I did notice the vacuum line off the egr was loose, and I tightened it. Could that little line have really made that big of a difference?

Try replacing all the vacume lines. And disconect/isolate and plug the line that goes to the Cruise Control Vacume Tank Resevoir if it is buried under the front bumper and not accessible. That line is commonly overlooked and is usually deteriorated. This could be a lean miss at highway speeds. Also check the exhaust manifolds between the runners as they usually have cracks and can start sucking air under different conditions and give false readings to the O2's.

Have you gotten into the ECM and watched live streaming data when it happens? Or do a snapshot when it starts to act up?

also isolate the vacume line that goes into the firewall that controlls the HVAC commands. Try and use a vacume pump on all the hoses and plug the opposite sides. There maybe a leak somewhere including a hardline or connector. The PRND switch also has a vacume line to it but I think its for the e-brake release.....

If there's a vac. leak somewhere, some shops have a Smoke Machine that taps into the vacume lines and pumps mineral oil based smoke throughout the system to find vacume leaks. Here's an article about finding vacume leaks: http://www.aa1car.com/library/vacleak.htm

The TPS Code is something that needs addressed. I have a 91 Eldo. I'll have to find my Fact. Serv. Manual and see what the diagnostic trees states. Maybe someone can post it up sooner.

I had the same experience in a turbo Buick. Turned out to be a collapsing sock on the fuel pump, discovered with real-time monitoring of fuel pressure using a gauge mounted on the outside of the windshield.

Is this car configured similarly? If so, the pump assembly is probably accessible via a plate on the top of the tank - perhaps there's even a trap door in the trunk.

Could be fuel pump wiring as well - just one bad/corroded connector and the voltage at the pump can drop considerably.

It sounded like an intermittant loss of electrical power or EGR to me. I hope that loose vacuum line was it. When the EGR acted up on my Buick , it would buck hard, just like turning the key off and back on. The wheel size difference may have an effect too but I don't have any experience with non-stock wheel diameters. It sounds like it would confuse the computer.

Im also having the same problem with my 93 deville at 35-50 the car stutters under light and medium acceleration it's got new wires,spark plugs, fuel filter, oxygen sensor everything in the last 3 months and last week I just got the trans rebuilt idk what the problem is please help!!! thank you everyone.