Ok, so I've got the bogging/hesitation/bucking/zero low-rpm power/etc issue, and it's getting so bad I could barely get home last night. I've posted on here before about this to no avail, and read threads about MAP whacks until I'm dizzy.

To sum it up: It's like the gas pedal is now "softer", and frequently useless at low RPM. 20% throttle is no different from 80%, for example. You push it in, not much happens, a few seconds later it usually "stumbles" and then "catches", and power is back to normal. Either that, or it just gradually feels like it's back to normal by about 5-6K RPM. I can tell the throttle is indeed opening though, because the exhaust gets louder (), but the lack of acceleration and power makes the pedal feel soft, as if I was towing an 18-wheeler. I hope that's a clear description of the issue.

I've owned the car for many years, I know what it should feel like, and it's still intermittent, sometimes it feels great. I've done the MAP whack (did nothing), I've changed the plugs (actually did seem better for a few days), oil is fine, air intake is clean, no CELs, the dealer can't replicate the issue. I've never experienced the issue at high RPM.

All signs still point to the MAP sensor (even though the dealer says that should throw a CEL), which I've cleaned (and hit) repeatedly. I haven't tried cleaning the passage leading to it, though (which seems logical). Anything else obvious that I'm missing?

Unless anyone here has any additional advice, I think I'm going to have to just start replacing parts until the issue is gone, which sucks. I'm going to do a brand-new MAP sensor first. Can someone confirm that this is part # 19483 on Majestic's site?

If that doesn't work, I'm going to try the TPS (throttle position sensor), since that makes sense too. Apparently that's bundled with the throttle body, and can't be purchased on its own? Is that true, and if so, is there an alternative?

Any help would be MUCH appreciated, I'm at my wit's end. Thanks!

 

Clean the electrical contacts for the MAP sensor and zip tie it in, if not done so already.

Clean the IAC valve then clean the throttle body (you will need to after the IACV...trust me).

I don't think you can get the TPS on it's own, only with an entire throttle body, I believe they are matched. A breaker may have one in stock.

Perhaps an O2 sensor is playing up too...although I would expect a CEL.

 

Check for vacuum leaks and make sure all your clamps are tight,

 

It may well end up to be the TPS. But try the new MAP and look for vac leaks.

Search Under the Hood...I recall a post within the past year where someone was able to replace their TPS only with some modifications.

 

Thanks for the replies, guys. I'll have a look today.

If it's a vacuum leak, though, wouldn't it always be bad? The intermittent nature of the problem is what makes me think electrical, not mechanical. Thoughts?

Majestic is as good a place as any to get a brand-new MAP right? Seems to be about $50 or so there.

 

All of the MAP issues I have seen are at higher rpm and throttle openings so I am more inclined to look elsewhere. Have you cleaned the throttle body?... I have seen build up cause problems.

 

Try replacing the VALVE ASSY, ROTARY AIR CONTROL (IAC) for $125 from Majestic. I had the same problems and replacing the valve worked for me.

Good Luck!

 

Cleaning it is cheaper and would be what I'd do in the first instance. You may end up saving that $125 for mods! This has sorted out similar problems for countless UK owners.

 

This is all great info, thank you guys so much. Keep it coming! I'm determined to get this finally fixed once and for all.

I had the same thought about MAP issues normally occurring at high revs, this is always at low revs.

So is replacing the IAC as simple as removing the old one and bolting up the new one?

Also - do you think it's just coincidence that changing the plugs helped for a few days?

 

Not sure about the plugs situation.

There's a thread in the FAQs for cleaning the IAC, removal/installation is a cinch, only a few bolts/hose connections. If you take a look it will become apparent.