91 B250 318 (5.2L) running rich, backfiring. Can't figure it out
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91 B250 318 (5.2L) running rich, backfiring. Can't figure it out
I have a 1991 Ram B250 with a 318 (5.2L). A couple weeks ago (and a couple thousand miles from home, no less) the water pump seal went, which caused the coolant to boil over and spray all over the engine compartment. It was driven for a few minutes after the leak started, and although it lost a lot of coolant, there was at least 4 or 5 litres in the engine block when I drained it to change the pump, so I'm assuming there's no engine damage.
Problem is that ever since then it's been running rich. I get puffs of black smoke if I give it throttle while idling. It hesitates at lower speeds and sometimes idles rough, though not always. Gas mileage has been horrible. At highway speeds I believe it backfires, you can feel the momentary loss of power and hear it through the doghouse. This happens especially when under load and climbing hills. It also shudders a bit at lower speeds, though not with any regularity.
So far I've replaced the air filter, O2 sensor, and coolant temp sensor. Nothing seems to help it. I was getting an O2 in lean mode code (51), but since I installed the coolant temp sensor I'm getting no codes. Distributor cap is good, contact points and rotor are good, dist. shaft isn't wobbly.
I took it to a shop but they didn't have a scanner to do 91s. They did tell me that they checked the EGR and the timing, and that both were good.
Any other suggestions before I take it to a dealer?
Problem is that ever since then it's been running rich. I get puffs of black smoke if I give it throttle while idling. It hesitates at lower speeds and sometimes idles rough, though not always. Gas mileage has been horrible. At highway speeds I believe it backfires, you can feel the momentary loss of power and hear it through the doghouse. This happens especially when under load and climbing hills. It also shudders a bit at lower speeds, though not with any regularity.
So far I've replaced the air filter, O2 sensor, and coolant temp sensor. Nothing seems to help it. I was getting an O2 in lean mode code (51), but since I installed the coolant temp sensor I'm getting no codes. Distributor cap is good, contact points and rotor are good, dist. shaft isn't wobbly.
I took it to a shop but they didn't have a scanner to do 91s. They did tell me that they checked the EGR and the timing, and that both were good.
Any other suggestions before I take it to a dealer?
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I have a 1991 Ram B250 with a 318 (5.2L). A couple weeks ago (and a couple thousand miles from home, no less) the water pump seal went, which caused the coolant to boil over and spray all over the engine compartment. It was driven for a few minutes after the leak started, and although it lost a lot of coolant, there was at least 4 or 5 litres in the engine block when I drained it to change the pump, so I'm assuming there's no engine damage.
Problem is that ever since then it's been running rich. I get puffs of black smoke if I give it throttle while idling. It hesitates at lower speeds and sometimes idles rough, though not always. Gas mileage has been horrible. At highway speeds I believe it backfires, you can feel the momentary loss of power and hear it through the doghouse. This happens especially when under load and climbing hills. It also shudders a bit at lower speeds, though not with any regularity.
So far I've replaced the air filter, O2 sensor, and coolant temp sensor. Nothing seems to help it. I was getting an O2 in lean mode code (51), but since I installed the coolant temp sensor I'm getting no codes. Distributor cap is good, contact points and rotor are good, dist. shaft isn't wobbly.
I took it to a shop but they didn't have a scanner to do 91s. They did tell me that they checked the EGR and the timing, and that both were good.
Any other suggestions before I take it to a dealer?
Problem is that ever since then it's been running rich. I get puffs of black smoke if I give it throttle while idling. It hesitates at lower speeds and sometimes idles rough, though not always. Gas mileage has been horrible. At highway speeds I believe it backfires, you can feel the momentary loss of power and hear it through the doghouse. This happens especially when under load and climbing hills. It also shudders a bit at lower speeds, though not with any regularity.
So far I've replaced the air filter, O2 sensor, and coolant temp sensor. Nothing seems to help it. I was getting an O2 in lean mode code (51), but since I installed the coolant temp sensor I'm getting no codes. Distributor cap is good, contact points and rotor are good, dist. shaft isn't wobbly.
I took it to a shop but they didn't have a scanner to do 91s. They did tell me that they checked the EGR and the timing, and that both were good.
Any other suggestions before I take it to a dealer?
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Joined: Feb 2015
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the water pump seal went, which caused the coolant to boil over and spray all over the engine compartment.
justmecruisin, do you have any codes? Two posts that should have their own thread.
You will get a 55 code either way.
https://www.allpar.com/threads/the-1...ost-1085223107
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Joined: Jul 2020
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From: Indiana
I'm not sure if the 91 is Throttle Body Injection or Multi-Port Injection, but my 89 with TBI had a bad fuel pressure regulator. It would pour fuel into the throttle body through the vacuum port in the tb itself. Mine was extremely bad. I replaced the fuel pressure regulator and the van ran smooth an as fuel efficient as it could.
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Joined: Apr 2010
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From: Clayton MI
I'm not sure if the 91 is Throttle Body Injection or Multi-Port Injection, but my 89 with TBI had a bad fuel pressure regulator. It would pour fuel into the throttle body through the vacuum port in the tb itself. Mine was extremely bad. I replaced the fuel pressure regulator and the van ran smooth an as fuel efficient as it could.
