bobnsue2 Posted March 17, 2005 Report Share Posted March 17, 2005 Our 91 Seville STS 4.9 has a new problem. First of all it passed the California smog test. (But, if allowed to idle too long, the hydrocarbons go up a bit high) Six months ago, I replaced the injectors and pressure regulator. It had been running fine since. I recently changed the oil and filter and air filter. Cleaned the throttle body which wasn't very dirty. Then disconnected the battery to do the relearn. Since then, when you first start it in the morning, it surges a lot until it is warmed up. It feels like it is choked down trying to stall, then the computer feeds gas so it speeds up and slows down for several minutes. There are no codes. I'vr been watching the diagnostic panel but don't really see what to deal with. I've taken a snapshot while it is acting up, but nothing obvious. Any ideas?? Thanks Link to comment Share on other sites More sharing options...
adallak Posted March 17, 2005 Report Share Posted March 17, 2005 Is your Idle Speed Control (ISC) motor original? I have already replaced it twice. It might be moving south. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bobnsue2 Posted March 17, 2005 Author Report Share Posted March 17, 2005 yup, ISC is original. 98000 miles. Is there a test that could show it up? Bob B Link to comment Share on other sites More sharing options...
adallak Posted March 17, 2005 Report Share Posted March 17, 2005 yup, ISC is original. 98000 miles. Is there a test that could show it up? Bob B Mine was changed twice at 76.000 and 141.000. Do you hear ISC motor making unusual noise when you shut the engine off? If you press ENG button on your DIC to see RPMs you can give as an idea about the dynamics of RPM while the engine warms up. The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bobnsue2 Posted March 21, 2005 Author Report Share Posted March 21, 2005 Yesterday I held the idle speed control with a needle nose and the choking then surging continued. So I don't think it's the isc. The injector diagnostics went fine, But I wish it would fail. At least then I'd know what the heck is going on.After it warmed up for 4-5 minutes it ran fine, smooth, and fast. Maybe the map is acting up? Bob B Link to comment Share on other sites More sharing options...
bobnsue2 Posted March 23, 2005 Author Report Share Posted March 23, 2005 I'm now wondering about the open loop and closed loop operation. The car only does the surging when cold, which would be open loop. It appears that when it is warmed up a bit it then runs fine so closed loop seems good. I think I'll watch the closed loop indicator on the DIC next time. Now what is the difference? Bob B Link to comment Share on other sites More sharing options...
bobnsue2 Posted June 13, 2005 Author Report Share Posted June 13, 2005 Well it appears to be fixed. Long story, but even after the dealer said it was the distributor, which didn't fix it and then they swapped the computer and that didn't help either. (they left the new one in because it cost more to remove it. They didn't charge for it either). When I got it home and it was still failing every morning, I tried adding grounds to the engine. I used my battery jumpers from the engine to the battery ground and also from the engine to the body. Then for 4 mornings tested it. It was fine. So I added a thick wire from the block to the ground screws near the battery and at the same time made sure the terminals were clean and not corroded. They were good. (this is a California no rust car). For 5 more days now it has been fine. Great news! I was ready to give it away. There are three screws in front of and behind the battery where 80 percent of the circuits terminate to ground. The other circuits end in the trunk for the rear bose speakers and the computer in the trunk for the ride control. Oh and by the way, On the DIC, the battery is now at 13.8 to 14.3 instead of !2.9 to 13.3 while running. Bob B Link to comment Share on other sites More sharing options...
Scotty Posted June 13, 2005 Report Share Posted June 13, 2005 WOW, ground problems again..... This is VERY similar to MATTS problems posted here http://caddyinfo.ipbhost.com/index.php?showtopic=6249 Link to comment Share on other sites More sharing options...
adallak Posted June 13, 2005 Report Share Posted June 13, 2005 Well it appears to be fixed. Long story, but even after the dealer said it was the distributor, which didn't fix it and then they swapped the computer and that didn't help either. (they left the new one in because it cost more to remove it. They didn't charge for it either). When I got it home and it was still failing every morning, I tried adding grounds to the engine. I used my battery jumpers from the engine to the battery ground and also from the engine to the body. Then for 4 mornings tested it. It was fine. So I added a thick wire from the block to the ground screws near the battery and at the same time made sure the terminals were clean and not corroded. They were good. (this is a California no rust car). For 5 more days now it has been fine. Great news! I was ready to give it away. There are three screws in front of and behind the battery where 80 percent of the circuits terminate to ground. The other circuits end in the trunk for the rear bose speakers and the computer in the trunk for the ride control. Oh and by the way, On the DIC, the battery is now at 13.8 to 14.3 instead of !2.9 to 13.3 while running. Bob B good job, bobnsue! I have been adding jumpers here and there for the last two years to keep her starting and running. I am planning a couple more grounds to the engine block (near the starter i saw a ground stud, pretty sure it is 8x1.25 mm). The saddest thing in life is wasted talent Link to comment Share on other sites More sharing options...
bobnsue2 Posted June 13, 2005 Author Report Share Posted June 13, 2005 Scotty, Yesterday I was telling a friend (Carlot owner) about the fix, and he said he just had ABS errors on a newish Mustang and even took it to a shop, but the shop couldn't fix it. So he cleaned the ground connections that he could find and it is cleared up also. Bob B Link to comment Share on other sites More sharing options...
bobnsue2 Posted June 13, 2005 Author Report Share Posted June 13, 2005 Hey Adillak, According to the shop manual, there are two grounds on the engine. One to the right of the starter, and one on the rear head right side. From the top I can't see either. But the one by the starter must be good because the starter is working fine, and it would need a good sized ground wire. The battery negative goes to there and also to one of the body grounds in front of the battery. I figure the engine therefore must be grounded to the battery. If anything was suspect, it could be frame/body to the battery, as the computer ground comes out to these ground screws near the battery, also the oxy sensors etc. ground there also. I will be changing the oil soon and will inspect/clean these two while down there. Bob B Link to comment Share on other sites More sharing options...
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