Ok, I'm cruising down the road about 40 or 45 and holding the pedal steady. Out of the blue, I feel this lag..like Im riding the brake, and then it lets off.. Lag...lets off. There's no change in the electrical output, or oil pressure.. And my tachometer is bad, but when I'm doing 40 mph and it does this, the RPM's fall off about 50-100. hn I'm doing 45, the tach is off to such an extreme extent that it can't register a fall-off that small, so there's no change. Keep in mind..that tach says I idle, on a warm engine, at 1500 at best. Cold engine idle at 2400. ;P So my question is guys..what is going on here? It feels like the car is letting off the throttle on its own and then going back down on it. I never change my pressure on the pedal when this happens. My cruise control has the same sort of problem. I set the cruise speed at 45..the car falls to 40, gasses it up to 45, tries to hold a steady throttle, but can't, and lets off it completely. I'm thinking bad sensor..what about you guys? Thanks.

BTW-My severe oil leaks are almost COMPLETELY fixed..thank *** .. Bad distributor o-ring! Can you say, "CHEAP REPAIR?!"

 

Have I stumped you guys or something? Where's the countless replies of dead-on-target help that this board is famous for?!

 

Me?
I'd check for vacuum leaks.
I have cruise on my 1985 S-10 Blazer.
Same type of design, different hook ups, since my engine is a carb.
Most of my cruise problem are now the vacuum hoses.
Especially he UNDERSIDE of the hose, as I cannot see that area, but, it's most vunerable to continueous engine heat. It gets all heat cracked and "aged".
I'd start there. Then maybe you may see other worn out stuff, due to aging.

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Chat Soon,
KED85
Karl
1985 Firebird 2.8 to 3.4 swap project for Smog Happy LA, CA

 

And the big question is... year of car, which engine, and which trans?

Other q's- Aftermarket tach or factory? Does this happen when the car's warm or cold?



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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

1991 RS with a 3.1 liter V-6 and the stock 700-R4 tranny. (To my knowledge.) My tach is factory and extremely defective, and my speedometer is going also.. And the problem has only seemed to appear on a warm engine. The cold engine doesn't do it when I'm running steady, but does have throttle cut-backs. Like, I give it gas and it jumps for a second but falls back, like I'm letting off the throttle, but I'm not.

 

Try this next time. When you hit the gas, and it "jumps for a second" and then "cuts back", keep your foot steady so the engine still acts like it's cut back. Now, use your left foot to press on your brake pedal lightly enough to turn on the brake lights, but not hard enough to slow the car. How's the car act?


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-Tom P (Hot rodded 1986 Firebird 2.8l)

 

Ok, I'll try that. I can tell you this..I was driving home going 35 with the auto overdrive on (I think)..and I tried the brake tap test. When I tapped the brakes while I held steady on the gas, the engine, for about 1 second, completely stopped any tone and noise it was making. After that second, the engine sound came right back. Now, I did this doing 45 in auto OD (once again, I think I was..) and nothing happened at all. Any of that help?

 

OK, I am NOT a mechanic, I can do basic maintenance on cars and thats about it, but I've seen or heard of this in a couple other cars. From what I understand from what you are saying, it sounds to me like the TPS, I may be way wrong, but it wouldn't hurt to check.

 

Yeah..I was thinking myself either the throttle position sensor or the oxygen sensor..but I never seem to run real rich or anything,so, I doubt the oxygen sensor.. Let's just see what the car *** known as TomP has to say..heh...

Don't let it go to your head, Tom..

[This message has been edited by Nixon1 (edited December 11, 2001).]

 

Just for your information, those 3 stars are for g-o-d...not @$$. This thing even blocks g-o-d now! Sheesh..

 

Just bringing this back up to the top again. I'm thinking the TPS.. I had the car in Drive today, and was holding it at 35 and did the tap test and nothing happened, btw.

 

I may have that same problem.. One day driving to school I had the cruise set at 55 and the car starts feeling like it loses power then get is it back a second later. It did it a couple of times and quit. I could hear the RPM's moving up and down too. It did it again later at 60 mph. It feels like it's in the tranny.

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2.8 mpfi
My only mod: Flowmaster 40 series
http://www.geocities.com/pita_j2000/MyFirebird.html?1002261961590
PICS ARE UP!!

 

Sounds a lot like me. But the tranny didn't make any funny grinding, thumping, etc. noises during this. But one time I experimented, and gave it some gas during one of the slowing episodes, and the tranny shuddered and shook like a POS before I started getting any acceleration out of it. But the shifting is good..I've never slipped out of gear. I never hang in any gear for too long, except 2nd to third..the car redlines for a second before kicking over. Although the tranny does feel like it's putting way too much effort into shifting, particularly downshifting. It's a pretty big jump when downshifting, and usually there's a funny brake-type sound, but more metallic..maybe that's characteristic of the late 3rd gen 700-R4's, I dunno.