Help..Can't get it to rev!

[YVRSpider]

Hi Guys,

I'm totally stumped and don't know what else to try. I've got an '82 Fi that I just did the timing belt, water pump etc on. The problem is that when the car is started (which it does easily every time) and I warm it up, when I try to rev it out, it just stammers and sputters after the 3500-4000 rpm range (sometimes makes a mild back firing noise at times too) and if I hold the gas right to the floor, it'll sputter and fluctuate between 3500 & 4500. So basically, with the throttle is floored and not moving it with my foot, the car seems to cycle on it's own in the 3500-4500 range but in a sputtering un-clean revving fashion fashion.
I've double and triple checked all the timing marks on the timing belt and they all line up perfectly. (Firing on cyl#4 as indicated by the distributor, crank pulley timing mark lined up with the 0 degree pointer and the two cam pulley's are lined up perfectly with the marks on the cam covers) I've changed the ignition rotor & distributor cap, 4 new plugs, new plug leads and checked the ignition timing and set it to 10o BTDC as per the factory manual specs. I've also changed all of the vacuum lines and the fuel pressure regulator. I've checked to see if the AFM is moving ok and it seems to be fine and tonight I cleaned out the Auxiliary Air Regulator and the fuel pump is new and is pushing lots of pressure from the tank to the FPR. I tried 2 rounds of Sea Foam and it made things a bit nicer at first but the fact is, I just can't get it to rev out in a nice, clean modulated way. It'll rev nicely down low but the minute it's demanded sputters and pukes. Any ideas or suggestions are greatly appreciated. Thanks very much.

[divace73]

Any chance there is air leaking that is unmetered (like a break in the rubber hose that runs from the AFM to the throttle body?)

[courtenay]

I'm with Divace on this one. I had a similar problem after I changed my timing belt and it turned out that I had not connected the big air hose to the AFM properly.

[YVRSpider]

Thanks for the input guys. I've been checking the air leak situation pretty closely but I think I'll go back and revisit all the connections and hoses one more time. Maybe even new hose clamps all around while I'm at it.

[narfire]

Try the propane gas thing around all the connections and see if you get an increase in engine speed.

[jfrawley]

Check the connection at the AFM. I had the same issue and it turned out it was caused by the connector not being seated all the way. Reconnected and all was well.

[YVRSpider]

Thanks Frawley, here's hoping its something as simple as that, I'll give it a try for sure.
Narfire: Hey Chris, not familiar with the propane thing but I'm game to try just need some quick instructions please.

[narfire]

propane thing... With a plumbers propane torch,not ignited, wave it around, with a little gas flowing, while engine is running near any hose connections and the shaft the throttle plate is on. Ie brake booster line, seal top and bottom of the intake plenum... Idea is if there is a compromised connection the propane will get inside and the engine will rev accordingly.
Watch for any open flame/ spark as propane sinks.
I'll put it near the intake air filter for a second to get a baseline of what to expect.

If all the connections are sound and hoses are not cracked, propane thing should not really be neccessary. I did put a leak down tester on my brake booster and did find it leaked allowing unmetered air into the intake. The leak made setting the idle virtually impossible(still is to some extent after swapping booster) but did run at higher rpms...opposite to your issue.
Chris

[courtenay]

"...it was caused by the connector not being seated all the way. Reconnected and all was well."


My problem was the same thing...

[vandor]

If the above things check out then you could have someone held it where it sputters, and measure the O2 sensor voltage with a DVM. That would tell you if it's rich or lean.

[YVRSpider]

Well, tried tightening all of the hoses etc but the problem still persists. I think I'm going to just bite the bullet on this one and have an FI tech look at it in the morning for me. I'll keep you all posted with the findings. Thanks a lot for all of the suggestions and help so far.

[courtenay]

Clemente's Autosports on Kingsway is an Italian car specialist if you don't already have a place to take your car.

[YVRSpider]

Thanks Bruce,
I've actually had a few good chats with Gio there and he'd been really good and helpful with his time. Appreciate the tip!

[narfire]

I've actually had a few good chats with Gio there and he'd been really good and helpful with his time

I talked to him yesterday.... he's sending a couple of shims up. Great local source of assistance.

[YVRSpider]

Ok guys, so here's what it was. Turns out that the fuel supply nipple on the fuel tank was plugged up with mineral deposits assumably from years of old/stale fuel and so the fuel pump just couldn't supply enough fuel from the tank causing fuel starvation to the engine.
Solution: Ended up removing the fuel tank and sending it to the rad shop to have it flushed out with an acid bath treatment, pretty amazing what came out of there but at the end of the day, its all good now and she's running fantastic. Thanks for all the suggestions and effort!