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Hello everybody!
My volvo is a 1990 740 GL Regina fuel system. 145,000 miles. I have recently gotten a job where I am now having to drive it around 70 miles a day to work and back. I have recently changed spark plugs, wires, timing belt & tensioner, transmission fluid and filter screen, radio suppression relay, all accessory belts, changed oil, fuel filter, and cleaned the throttle body.
The car has always dropped to about 500 rpms when shifted into reverse when the engine is cold. However, recently I have been giving it gas in reverse to back out of my parking space & when I let off the gas it will stall out. I can work the brake & gas to keep the engine rpm up when shifting to forward, but it will stall out without any extra help. After that, it idles fine. I get in the interstate & it runs normal. After driving 32 miles, when waiting at the traffic light at the off ramp, it idles at about 500rpms & is very rough. When I go to give it gas again, it drops rpms but then surges back to normal driving rpm. If I put the car in neutral or park at this time, the idle surges between 600-900rpms.
When leaving work, everything acts normal.
I had what almost seemed like a miss when idling, so I cleaned the throttle body & put fuel system cleaner in the tank. That fixed the miss, but now it is doing what I described above. After the throttle body cleaning, my idle speed was adjusted correctly.
It also has a low sounding misfire when coasting on the interstate, which I know could be a rich condition. However no codes are on the obd system. I had a code months ago that referenced the O2 sensor, but that hasn't come back. Is this related to the idle problem?
I replaced my transmission fluid & filter because I had a whining sound that would wind down as I slowed down. My shifts smoothed out & the whining went away. I had a slight leak in the hose that goes into the side of the pan that I have since fixed, but I think I slightly overfilled the transmission when topping it off. Now my shifts are harsh again & the whining sound has come back. Could this have anything to do with the idle?
I know I'm getting close to the mileage where I need to change my fuel pump.
Does anyone have any clue what my problem/problems could be?
Thanks,
Ben
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I had the same issues on a 92 740 Regina and it turned out to be the map sensor itself. After fixing the vacuum elbow at the map sensor I too thought the problem was gone. If you decide to buy a new map sensor, auto zone sells a TruGrade brand for 41 bucks. The part number is SU105T6. Its actually a GM replacement MAP sensor. I cleared the codes for the OBD and all is well. Hope this helps!Larry
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Hey everybody! I went ahead and replaced the MAP sensor as well as the two rubber elbow pieces because they were shot. That made the car run slightly better, but still didn't fix my problem. I also took off my cap & rotor and cleaned them. Neither looked very worn. I then replaced my throttle body gasket with a new one, since I neglected to do so when I cleaned it. Next, I tested voltage at the ECU for the ECT sensor. Right after shutting the car off, it read 268 ohms. That is in spec for a car at operating temperature.
I also tested the air temperature sensor in the air intake hose. I got a reading of 2.15k ohms, which seems to be about correct for 34 degrees outside air temp when you take into account a hot engine bay.
I also switched coil units out because I had a spare, and the problem didn't improve. I checked my flame trap, replaced the trap, nipple, and the hose that goes from the intake hose to the flame trap due to suspect cracks.
After replacing these parts, the car runs a little bit better. However, I still have what seems like an erratic miss or stumble when at idle. It does not matter whether the car is in gear or not. The stumble still occurs. I was convinced that it may be a dirty or dead IAC valve again, but the erratic miss/stumble still occurs when accelerating from a stop up to about 5mph. So the IAC is deactivated by that point.
Does anyone have any other suggestions? The car runs great at speed other than slightly lower gas mileage. I listened for vacuum leaks, but couldn't hear or spot any.
Thanks,
Ben
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Hello again everyone! So my volvo is still doing the same very low rpm at about 400-500rpms in gear & surging from 700-900rpms in park or neutral. No codes on the obd system at this time. I sprayed wd-40 around all of the fuel injectors, intake manifold gaskets, throttle body gasket, all vacuum fitting & there was no change in the very low idle speed.
However when I went to read the obd codes from socket #6(ignition), as soon as I pressed the button the rpms dropped from the surging 700-900rpms down to about 400rpms until it was done flashing a 1-1-1 at me. After the code reading was done, the engine went back up to a 700-900rpm surging idle again. Does anyone know if this occurrence is significant or is giving a clue?
My only guess is that it is ignition related, because the rpms didn't behave the same way when reading codes from socket #2.
Again, the car runs normal until you are idling when the engine is warm. Cold start & idle is normal.
Please help!
Thank you,
Ben
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Hi Ben
The OBD1 code reading is meant to be done with the key in KP2 with the engine not running. I have no clue what checking the codes with the engine running would do/change. Main suspects for such idle issues are IAC and proper adjustment of throttle linkage in relation to TPS. See FAQ'S, You must make sure the TPS switch clicks just as the butterfly opens and again just before it seats on wall of Throttle body. Also when the idle is low, try tapping on the IAC with a small wrench or such and see if Idle raises.
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Okay. Thank you for the reply. I was just unsure of why the idle dropped when reading the codes. I have done it in the past with the engine on and with the engine off. It always read the codes the same way on or off without an rpm drop before. Even with the engine running, the key is at KP2.
I have cleaned the throttle body and made sure that the tps clicks just as you put a little bit of resistance on the linkage when I reassembled everything. I will tap the IAC later on tonight when it is running poorly to see what that does.
I'm wondering if I didn't clean the IAC well enough when I took it off the engine.
As it stands now, the engine only runs poorly when it is warmed up to normal operating temperature.
Also, I can usually achieve 200 miles before my gas gauge reads half. On my last tank, I only made it to 180 miles before I was at half. This morning, I only drove 160 miles before I was at a half tank of gas. So my MPG is getting worse & worse.
I am wondering if it may be my coolant temperature sensor, my map sensor going bad, or an intake manifold gasket leak.
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So I went and drove the volvo around a loop in my neighborhood, and I could barely keep it running. It died 8 times on me in the 0.6 mile loop i drove. I cleared the codes before I started it up again and 232 and 121 popped up as soon as I started driving.
I think I was wrong earlier in my code reading. I wasn't reading from the Regina code chart. 1-2-1 on a regina car is "signal missing or faulty to/from pressure sensor" with the MAP pressure sensor being the source of the fault. 2-3-2 is "self-adjusting oxygen sensor not operating" with intake air or fuel system being the fault.
So I think I need to break out my volt meter & test the voltage on the MAP sensor connection?
I only got the map sensor fault once, but I have gotten the O2 sensor fault many times.
Thanks,
Ben
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Ahhh yes. I have made similar mistakes looking at the code tables. The Map sensor code is typically not the sensor itself but the rotting rubber vacuum hoses that attach to it. Check/replace vacuum hoses. 02 sensor testing is covered in FAQ's.
I would mention two items regarding the IAC. It fails in the closed position, sometimes if you take a wrench or such and give the body of the IAC a good whack, while its idling low, it will free up and you will hear the idle return to normal(temporary).
If you pinch off the hose that goes from the IAC to the manifold(feed), if the IAC is working the idle will drop when the tube is pinched closed.
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We've got a winner! You were right about the dry rotting rubber vacuum hoses coming out of the MAP sensor! I checked the MAP sensor out and noticed the white tubing was slightly dislodged & situated near a torn part in the rubber boot. I was able to shove the tubing further up in the MAP sensor boot & the idle smoothed out and the car started to run great! So my problem is fixed! Thanks for all of the suggestions guys! That's why I always come back to this forum! Everyone is willing to help a stranger out & many people are a lot more knowledgeable than I am!
Do you think the small backfire problem I have while coasting on the interstate is related to my O2 sensor reading incorrectly & making the car run rich? I will do the O2 sensor checks from the FAQ to see if mine is working correctly.
Thanks a lot!
-Ben
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Items to check:
1. When you replaced plugs and wires, did you also check/replace the distributor cap and rotor ?
2. Check for intake manifold gasket leaks. Listen with a mechanics stethoscope or rubber hose. Spray WD40 around the gasket and see if the idle changes.
3. Confirm that all hoses connected to the IAC valve are in good condition with no leaks. Even a small leak due to a slightly cracked or loose hose can affect the idle quality.
4. Check the large air hose between the pressure sensor housing and the throttle body for cracks.
5. Make sure there is no corrosion in the electrical connector on the IAC valve and the mating wire harness connector. My 1993 940 randomly stalled, the problem was caused by slight corrosion in the IAC connector.
6. Check the fuel pressure regulator on the fuel rail (See FAQ).
Mike
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1.
I checked the distributor cap & rotor when i replaced the plugs & wires. Everything seemed to be in good shape. the cap & rotor were replaced at 95,000 miles about 10 years ago.
2.
I will spray some WD-40 around the intake manifold gasket soon to see what that yields. I see no obvious leaks though.
3.
When I cleaned the IAC valve tonight, I took both hoses completely off and inspected them for leaks. They were leak & crack-free!
4.
I'm not exactly sure which hose that is. But I will research it. What is the general diameter of this hose I am looking for. This is the larger of the two hoses coming off of the throttle body I assume? When I cleaned the throttle body last weekend, all hoses looked to be in good shape.
5.
I checked for corrosion on the IAC connector and plug tonight. Everything looked clean & corrosion-free.
6.
Fuel pressure regulator is fairly new. I took the front hose off & found no drops of excess fuel. Cycled the fuel pump with the hose disconnected & no gas came out, so I assume it is in good shape?
I will check the intake manifold gasket soon & let you know. I have to go buy another can of WD-40, as my current can just ran out!
Thank you for all of these ideas!
-Ben
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1. Cap and rotor need replacing, probably plugs and plug wires also. Only use quality Bosch and Bougicord items, NGK Copper plugs.
Does the IAC work when 12 volts is applied?
Dan
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I cleaned the IAC. As soon as I put it all back together, the car still ran rough & threw obd code 223. 223 is the code for no signal from IAC. So I thought I had broken my IAC valve while cleaning it. I then ran through the obd diagnostic mode 3 for three times & I could hear the IAC valve cutting on & off. So I at least know that it's still opening & closing.
I restarted the engine. Now when I run the engine, I don't get any codes, but I have to keep my foot on the throttle to keep the engine from stalling out until the car gets warm. Eventually, as I started to lift my foot off of the throttle the engine suddenly jumped up to 1000 rpms. It started bouncing between 800-1000rpms consistently. In forward & reverse, the rpms are steady at 700. After idling for a while, the check engine light came on and codes 232 and 221 came up when running the obd diagnostics. Would those codes be pointing to low fuel pressure or a fuel pump? Does anyone have any ideas?
Thanks,
Be
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Thanks for the replies!
I'll check to make sure my throttle body makes a click noise when I just begin to turn the linkage. I know that it was when I reinstalled everything the other day.
Do you think throttle body cleaner will work to clean the IAC valve out, since I have about half a can left? I've heard it's not as harsh as carb cleaner, so I was wondering if it would be as effective cleaning everything out.
I ran obd test mode 3 I think where it fires off various sensors & I heard the IAC open & close several times, but that was 2 months & 3000 miles ago.
I will clean it out after work today & let y'all know the results later on.
I'm guessing my slight backfire while coasting downhill on the interstate is not related to this idle issue?
Thanks,
Ben
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I agree with The Rod, I'd remove the IAC valve and spray some cleaner in there, it sounds like it's sticking. Running thru the throttle position setting procedure couldn't hurt either, though I've never found it to be a problem on my 93 Regina 940.
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9 times out of ten an idle problem on a 740/940 is related to the IAC valve(failing or wiring issues) or the TPS(bad switch or more likely maladjusted throttle linkage). See FAQ's for details.
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