QuestionQUESTION: Hi, just bought an 82 xjs fuel injected. The car kicks over with no issues but after idling for 30 secs or so stalls. If it doesn't stall when you put it in drive and give it gas it bogs down. No misfire or backfire is heard. Car sat in a barn for three years. satrted up with almost no issues. Runs fine till you give it gas and runs great if you get it over 40 mph. Any ideas where i should start looking? This is a beautiful car in awesome shape with this one issue.
ANSWER: Hi Pedro,
Your symptom does not indicate what is wrong. So you need to start testing. I would first try to rev the engine from idle and if it stalls then or hesitates try spraying some starter fluid in both intakes just before you rev it up to see if that helps. If it does first test the fuel pressure at the time of the hesitation to see if it is a fuel supply problem (fuel filter).
Did you drain the stale gas out of the system? That is also a symptom of stale gas. Also run some injector cleaner through the system and clean or replace the plugs also.
That is a starting point.
Howard
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QUESTION: Hi Howard,
Have changed fuel filter and removed old fuel and put new hi grade fuel in. Added Sea Foam to gas but have only managed to get a 1/4 tank through so far. Haven't checked plugs but thought if there was no mis/backfire that the plugs would be ok. Again she only bogs when i want instant power, she will get to speed if I feather the gas but if i step on the gas to hard she starts coughing bogging.
Thanks
AnswerPlugs can do that so don't leave stones unturned just because a plug problem normally causes a miss and backfire. That has bit me more than once (leaving stones unturned).
I thought you said over 40 was ok? Now you need to "See" fuel pressure at the time it bogs with hard throttle. I would also run a long hose out from under the hood with a manifold vacuum gauge on it and put the gauge under a wiper arm so you can see vacuum under hard throttle settings. Steady full throttle with full load should not go below 5 in hg. If the vacuum seems to go to zero and then it starts to bog you should check for exhaust back pressure. Most cars can't handle any more than 1.5 to 3 PSI. If it is a problem you will see 5 to 7 PSI at the time of bog.
I have tested many cars but not an "S" so I can't tell you how best to connect the gauge. Possibly remove the O-2 sensor and make a temp adapter for your gauge. On cars that it is difficult to get a hose connection some mechanics just separate the pipe about a half inch or so and make a quick run.
Have you had it tested for HC / CO yet? Generally high HC is either an electrical problem or a mechanical problem and CO is fuel mixture. This will at least tell you in which direction to test.
Howard
