Mykl

After changing my fuel filter, spark plugs, and oil tonight I decide to go out for a drive to see how she ran. In addition to all that I have a bottle of fuel system cleaner in the tank that I poured in on Tuesday. I don't have the power steering belt on because I broke the tensioner bolt two days ago, but I have all the rest.

First couple runs to redline in first and second gear were wonderful. She pulled hard and smooth all the way to the rev limiter, exactly how the car should run. In fact, usually I notice power dropping off a bit before redline, but tonight even after hitting redline she just wanted to keep pulling harder and harder.

After a couple runs I noticed that the car would hesitate a tad near the top of the RPM range, and didn't pull like it did for the first couple runs. She wouldn't hit redline as hard, and certainly didn't want to keep going all the way to the rev limiter.

I've also got some crazy popping in the exhaust when the engine spools down when it's not in gear, it's really annoying. It also bucks in any gear when I go to off throttle to on throttle, that's really annoying too.

When I got back I checked my belts, and again, the A/C belt fell off. I really don't get it, am I not tightening it enough? Should I just keep tightening the **** out of it until there is zero deflection? Is it possible that the belt is too wide for the pulleys? I really really don't understand why these belts don't want to stay on, but the belts I had that came with the car didn't fall off until one of them literally snapped.

Any advice on my cars "quirks" would be welcome.

takerwolf

Not sure about the belts, but as for as the deceleration problem, warm up the car all the way and take off the intercooler if you have a turboII. Then unhook the throttle sensor and put an ohmmeter on the top and right prong. Turn the screw with the spring on the throttle to the left of the TPS until it is about 1,000 ohms (It must be at normal operating temp with the car off to do this). Then there is a round thing with a white rod sticking out of it (dashpot), open the throttle till the rod seperates from the throttle and see what the ohms on the TPS is, it should be between 1,800 to 3,800 ohms, if not turn the dashpot till it is and set the lock nut. What the dashpot does is it makes the car decelerate slower and more smoothly. Let me know how it turns out.

Mykl

My ride is an '89 convertible, it's in my sig. No big deal though, you still gave sound advice on adjusting the TPS. Thanks for the reply, for a while I didn't think anybody was gonna touch this post.

I don't know if I mentioned it or not, but I fiddled around with the TPS and an ohm meter tonight. The n/a TPS' have a six pin connector. At closed throttle if you measure the resistance between the two on one end you'll either get ~1.00 ohms or ~4.00 ohms. Open the throttle and the numbers reverse themselves, the side that was ~1.00 now becomes ~4.00 and the side that was ~4.00 becomes ~1.00.

In the past I've gotten great results by matching the low range numbers. Meaning, at closed throttle the side that reads ~1.00 should match the reading you get from the other side at wide open throttle. Oddly enough, adjusting the TPS had no effect on the popping or the bucking so I just set the low range at 1.00 ohms for the time being.

I've also disconnected the spring on the fast idle cam and wired the linkage back, so the thermovalve has no effect on the throttle position while I'm attempting to set the TPS. I'm using this as a band-aid because my thermovalve is malfunctioning. For some reason it isn't getting enough water to open all the way when warm, causing the fast idle cam to keep the idle higher than it should be when warm.

I've also tested the TPS to assure that it is still good. There were no spikes in the resistance, so the TPS is fine.

I think the bucking problem lies in the adjustments to the linkages on the throttle body, but I'm unsure of how I need to adjust it in order to get it to where I want it. I may have tomorrow off of work so I might pull it off and turn some screws to see what happens. What I'm curious about is what effect it will have if I open the throttle plates a little more. My theory is that I don't have them open far enough and the throttle is opening late. So when I go from off throttle to on throttle the TPS tells the ECU that the throttle is opening, so it injects more fuel into the engine. But the since the throttle plates are opening late it isn't getting as much air as the ECU expects, so the car bucks when it goes from being rich to normal. This is only my theory though, I have yet to play with it.

I think the popping problem has something to do with the ACV, maybe it's gummed up or something. The popping on deceleration is actually the engine backfiring a bit, right? So if the ACV isn't sending the air to the engine to fully ignite all of the fuel in the engine, the detonation is going to spill out the exhaust. Oh, the popping doesn't happen at idle, only if I hold the RPM steady at a higher RPM than idle with the clutch disengaged (say, holding the engine at 4000 RPM's and it pops) and on engine speed deceleration.

The car idles fine, usually at ~700 RPM's depending on what accessories I'm using and it's not in the habit of stalling when the A/C kicks on or I'm using the power steering. It has happened before, but only on very hot days when the A/C is on full blast and I turn the steering wheel from lock to lock. It's only flooded on me once, but it fired right up after I stomped the gas pedal to the floor to cut off the fuel pump for a moment.

Oi, sorry for the length, but I was hoping that I could get a few comments how accurate my analysis of these annoyances are.

Oh, and the engine only has 40k miles on it.

Mykl

I forgot to mention something...

If the car is in gear and I slowly go from off throttle to on throttle there's a very brief period just before it bucks where the engine sounds different. If I touch the touch the throttle in just the right way I can make it make this noise as long as I want. The noise is a little lower than normal, then when I push the throttle in more it then bucks.

The car doesn't accelerate when the throttle is at this point, and as far as I can tell the engine may not even be firing but spinning only because it's in gear and the car is rolling.

At this point is where I think that it's running so rich that the plugs can't fully ignite the gasoline. I changed the spark plugs last night and the leadings look fine, with only a couple black sploches. The trailing plugs look black though, like it's running rich.

takerwolf

I have the 87 factory service manual, and most stuff should be the same, so if you need to know how to check anything let me know. Does the hesitation happen around 3800rpm by any chance?

Mykl

Nope, the car sails past 3800 RPM's with no problems.

The hesitation was at high RPM's, above 6500 RPM's and it was hardly noticeable. More like the engine just wasn't pulling as smoothly as it should have rather than hesitation.

What puzzles me is how my first few runs to redline the car hauled like a train all the way to the rev limiter, it actually accelerated harder once I went past the redline. I didn't know the car was capable of that, it was just so smooth and progressive. Usually the car does what it did after the first couple runs, power begins to drop off a tad after 7500 RPM's to the point where I have to shift at redline.

Thanks about the FSM. I have a .pdf copy of the '88 manual available to me so I won't need to bother you with anything. I really wish I could find a copy of the '89 manual on the net somewhere. I have a copy of the '88 and the '93 right now.

takerwolf

try jumping from the battery to the bac valve and listen for the noise of it moving