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Discussion Starter #1
4.5 litre 89 sedan deville. Stumbles and hesitates only when transmission is in gear. When driving down highway or taking off the car will stumble and hesitate but when I put it in neutral the engine runs fine. For example I was doing 40 mph and it started to stumble so I immediately put it in neutral and the engine ran fine. Is there a switch on the transmission that I should look at replacing to resolve this problem? If this was an ignition problem then I would think that when I put it in neutral the engine would still stumble but it does not. It runs perfectly. Any Cadillac specialists out there that can tell me what is going on? Replaced, wires, egr, plugs, rotor, distributor.
 

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2010 CTS (Elvis) 1964 Impala (Betty) 1991 Miata (Dolly)
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A good first step would be to check for codes. My '91 De Ville was stumbling and lurching, too, and I replaced the fuel injectors with new ones from FiveOMotorsport. That took care of the stumbling under load, but my car continued to stall. The OBD codes told me the camshaft position sensor (inside the distributor) was bad, so I replaced that. But the car still stalled, and I got codes for no distributor signal and distributor signal interrupt. So I replaced the ignition control module, and thankfully, my car is running fine now.

Several others on this forum have used the fuel injectors from FiveOMotorsport and recommend them highly. I'm no Mr. Goodwrench, but the problems with your car sound familiar to my own.

Hope this helps.
 

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Discussion Starter #3
Check for the injectors and they do not list 89 cadillacs and also my car does not stall. Why would the injectors be bad only under load. I sit and put it in drive and brake torgue it and it runs fine. Where else do I look for 89 cadillac, 4.5 litre injectors? Also what does the camshaft position sensor and ignition control module do? Are they easy to change?
 

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2010 CTS (Elvis) 1964 Impala (Betty) 1991 Miata (Dolly)
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If your camshaft position sensor is bad, it should throw a code. Both the cam sensor and the ignition control module are under the distributor cap. The module is an easy swap, but the bolts for the cam sensor are impossible to get with a 1/4" socket. You'll need an open-end wrench, and there's not a lot of room to turn it.

BTW, the cam sensor is also known as a hall effect switch.

I'm not sure why the fuel injectors for an 89 4.5 would be different than those for a 90 4.5, which FiveO does carry. Might be worth a phone call.

Sorry I can't help any more than that.
 

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Discussion Starter #8
The plug wire and the plugs and the egr and the rotor and the distributor cap are all AC Delco parts and all new within the last week. All gapped properly etc. etc. What I don't understand is if it is an ignition issue then why does it only stumble during the transmission under a load. I would think that if it is a back sensor it would happen both when in neutral, during a neutral acceleration and then under load. Helppppp!!!!!
 

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Sounds a lot like a problem I had two years ago with my 85 Seville. Car ran fine during idle or just cruising on a level street but once it started going up a hill it would stumble and vibrate so badly that I wondered if it was going to quit on me. The problem started showing up a week or so following a tune up. I took the car in to my mechanic, a well respected caddy mechanic here locally. He gave up in disgust after about 2 days of troubleshooting. They replaced the wires, coil, and plugs trying to fix it but no dice. So I wound up just driving the car that way for a couple of months. The problem finally "fixed" itself...sorta. Someone broke into my car one night and stole my aftermarket stereo. It was a pioneer model rated at 45W x 4. Problem magically disapeared! I reinstalled my stock radio and the car still runs fine to this day. I still have no idea what was reallly causing the problem or why pulling the pioneer stereo seemed to fix it. I didn't hack any wires in the radio's harness I used an aftermarket adapter made for the car. Go figure!??
 
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