Re: '91 4Runner bogs severely when cold..

1st - Don't clean the K&N so often. The dirtier the filter is, the better if filters. It actually uses dirt as a filter media. Personally I would let it go for at least 45k between cleanings. A common problem to look out for after cleaning is the oil from the filter coming off and coating the mass air meter element. This alters the reading it gets and it ends up telling the computer to add fuel incorrectly. I don't know your exact meter configuration, but on V8 Mustangs you can remove the element if your careful and clean it with a gentle blast from a can of electronic parts non-residue spray cleaner. The elements are extremely fragile so be very careful. Some people use a Q tip and alcohol to clean it but I wouldn't recommend it due to how fragile it is.

2nd - Combustion is three things, right? Fuel, spark, compression. You've verified spark with the Jacob's ignition diagnostics. The plugs are stock, but have you verified the plug gap? You could play with the gap a little. Tighten it up a hair if you think your spark might be weak. I really don't think you'll find anything there but it won't hurt to play with it. Just put it back to stock gap if you don't find any difference because you could be loosing mileage or spewing more emissions out the exhaust. As for compression, that might be one of the biggest problems you have. The key word is might. The rings will seal better as it warms up so that will cause a difference right there. What about your injectors? 205k miles on the stockers? You can get them cleaned, rebuilt and flow tested for ~$11 per inj at

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. I would think that the poorspray pattern of an old injector would be more critical on a cold enginebecause the heat helps to atomize the fuel. The worst thing here is havingthe car down for a few days while you wait on them to get there and back.

'91 4 Runner, 3VXE engine, 205k miles. Compression is gettin' low, > but cylinders are even. Oil consumption is about a quart between > changes (3k miles) > > It recently began bogging severely when cold. Almost as if the > ignition were being turned off and then back on. It's got a Jacobs > OmniPack on it as well as a set of Jacobs 8mm wires, K&N FIPK. > Downey headers, DynoMax muffler and 2.5" exhaust > > I've checked the entire intake from the filter back to the throttle > body. I don't see any obstructions or leaks. Header bolts are tight > and assorted Air Vent/EGR plumbing is secure. FIPK element is only 2 > months old and was cleaned/re-oiled at the last oil change (about 3 > months ago) > > Plugs are nice tan in color (Stock NGKs here) and the wires look to be > in good shape. Cap and rotor look pretty good as well. I took the > Jacobs ignition out of the loop by removing the dummy load from the > stock coil and connecting the stock coil to the dist cap. Problem > persists. > > Pulled the cold start injector and tested it. It tests fine as does > fuel pressure. Checked ignition timing and it's right on the money as > is idle RPMs > > I'm at a loss as to what could be causing this as it runs good once > it's warmed up. A tad down on power, but hey, it's got 205k miles on > it. :) > > I've seen similar problems on my 4 wheeler (ATV) when the air cleaner > is dirty or I've got too large a pilot jet in the carbs, but again, > filter element is clean and I don't have any jets. :) > > Anyone got any ideas?? This is drivin' me nuts.. > > > TIA
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Bard
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