1988 Toyota Pickup Loss of hiway mpg, sluggish performance

Tiny
DDCLEMENTS
  • MEMBER
  • 1988 TOYOTA PICKUP
  • 4 CYL
  • 2WD
  • MANUAL
  • 225,000 MILES
Hello,
I rebuilt the top end of my 22R engine in my 1988 Toyota truck 4500 miles ago. It included a new head, new RV cam, new valve springs, 4-angle valve job, new head bolts, new timing cover, new timing chain, new cam sprocket & crankshaft sprocket, new timing chain rails, new oil pump, and a new catalytic converter.
I have had the valves adjusted at a local Toyota dealership. The engine idles with 19" of steady vacumn(900' elevation). The idle is very smooth at 750 RPM, and the compression is #1 cyl.-174lb, #2 cyl.-175lb, #3 cyl.-175lb, #4 cyl.-180lb. On a cold engine. All spark plug leads check out with about 0.5 Ohms of resistance. Plugs are NGK #BPR5EY.
I rebuilt the carburator about 3 years ago and it was giving outstanding mileage(31 mpg hiway) prior to this engine rebuild. The engine uses no oil between oil changes.
Here's the problem: #3 spark plug on multiple examinations is always coming up way richer than the other 3, even when I have switched it's position in different cylinders. I have lost 5 mpg on the hiway. The engines performance seems doggish as compared to the factory standard camshaft. I have tried 2 different ignition timing positions: 2 degrees BTDC and 7 degrees BTDC. The factory setting is suppose to be 0 degrees BTDC. At this setting it is a very smooth idle, but it is also very smooth at the other two settings. Even at 7 degrees BTDC I don't notice any pinging on hard acceleration on hills. The distributor has the 2 vacumn line setup. I talked with the machine shop owner where I purchased the new parts about this problem and he said this is not the usual scenerio with the RV cam in the 22R engines, as most people have reported slight mpg gains and better performance. Thank you.
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Sunday, March 1st, 2009 AT 12:27 PM

13 Replies

Tiny
RACEFAN966
  • EXPERT
Ok so does you truck have a computer onboard? If so then you will loose mileage as the computer can not compansate for the larger cam. Now I would see if anyone happens to sell a wide band O2 sensor for this truck this may fix your problem. How does the carb adjust out? Have you adjusted it yet? Get back to me and we will go from there.
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Monday, March 2nd, 2009 AT 7:47 PM
Tiny
DDCLEMENTS
  • MEMBER
I talked with Delta Camshaft, the company that manufactured my cam and they said no adjustments are necessary with my computer(the vehicle has a computer) with the RV cam. It is a 260 degree duration cam. Also I have installed a new Oxygen sensor and he said a wide band one is not necessary on this engine. He stated that this cam has been widely tested with the 22R engine and it should not be giving poor mileage if all is working properly. Could the EGR be a possible reason for a rich fuel mixture in #3 cylinder?
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Tuesday, March 3rd, 2009 AT 11:52 AM
Tiny
RACEFAN966
  • EXPERT
Ok Delta is a great company and do great work. So with that I would have to say you have some carb problems. So I would check the cap and rotor and ohm out the spark plug wires and what gap are set on the spark plugs? Get back to me with what you find and we will go from there.
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Wednesday, March 4th, 2009 AT 10:28 AM
Tiny
DDCLEMENTS
  • MEMBER
I already have checked spark plugs, switched plugs, ohm'd out ignition wires, rebuilt the carb 3 years ago. Where do we go from here?
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Monday, March 9th, 2009 AT 10:39 AM
Tiny
RACEFAN966
  • EXPERT
You do have the distributor in time not 180% out right? Have you checked the fuel pressure to see what it is doing?
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Monday, March 9th, 2009 AT 4:28 PM
Tiny
DDCLEMENTS
  • MEMBER
#1 cylinder is firing when it should and the distributor is not out 180 degrees. This engine has a mechanical fuel pump. It is getting fuel. What next?
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Tuesday, March 10th, 2009 AT 1:22 PM
Tiny
RACEFAN966
  • EXPERT
Ok it is getting fuel but do you know what the fuel pressure is? What color is the spark at the plugs?
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Wednesday, March 11th, 2009 AT 11:00 AM
Tiny
DDCLEMENTS
  • MEMBER
Well, I have no way of checking the actual pressure of the fuel pump, but the pump is only 2 years old. As to the spark plugs, #1, 2&4 are coming out very light tan color while #3 is coming out black, even when switching the #3 plug with another plug. #3 cylinder is not burning as clean.
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Wednesday, March 11th, 2009 AT 1:39 PM
Tiny
RACEFAN966
  • EXPERT
Well that say's that the engine is getting to much fuel. So if it will not adjust out right it may need to be gone through again as much as I hate to day that. Now what are the ohm's on that plug wire and how long is it? The ohm's should be less then 25,000 per cord.
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Thursday, March 12th, 2009 AT 10:12 AM
Tiny
DDCLEMENTS
  • MEMBER
The ignition wires are summit racing, and all check out with.5 Ohms of resistance. With almost 19.5 inches of steady vacuum at idle on a warm engine, I believe the engine is mechanically sound. What next?
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Tuesday, March 17th, 2009 AT 12:21 PM
Tiny
RACEFAN966
  • EXPERT
Well if all that is good and the fuel pressure is good then it must be a carb problem. I must assume that the valves are adjusted right and the intake manifold isn't leaking anywhere so that leaves only one thing left carb. Have you considered a Webber carb? I know they aren't cheap but with all that you have done it will only make the improvements that much better. Your call there but carb is where I would be looking now.
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Wednesday, March 18th, 2009 AT 10:09 AM
Tiny
DDCLEMENTS
  • MEMBER
Well, my 1988 Toyota truck is back in fine form. I have fixed the problem that was causing poor mileage, lack of power, and generally sooty exhaust. The problem was not time consuming to repair or expensive. And was a very simple malfunction with very significant negative performance results. I just checked my city mileage and got 25.1 mpg. That is almost 6.5 mpg better than when the problem was present.
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Tuesday, April 14th, 2009 AT 8:20 PM
Tiny
JIRVINGG
  • MEMBER
I have the exact same problem with my 22r in my 1989 toyota pickup. I also installed a performance cam and new timing chain etc and now have the exact same issues as you did. What was your solution? Thanks.
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Thursday, January 23rd, 2014 AT 7:05 PM

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